Ethylene copolymer, thermoplastic resin composition containing same, and process for preparing ethylene copolymer

ABSTRACT

Ethylene copolymers are disclosed herein which are each derived from ethylene and an olefin of C 3  to C 20  and in which any quaternary carbon atom is not present in a polymeric main chain; the activation energy (Ea) of melt flow is in the range of 8 to 20 kcal/mol; and (1) a ratio between a Huggins coefficient (k 1 ) of the copolymer and a Huggins coefficient (k 2 ) of a straight-chain ethylene polymer having the same intrinsic viscosity meets the equation 1.12&lt;k 1  /k 2  ≦5, or (2) a molar ratio  CH 3  /CH 2  ! of a methyl group to a methylene group in a molecular chain is in the range of 0.005 to 0.1, and the equation Tm≧131-1,340  CH 3  /CH 2  ! is met, or (3) Mw and a die swell ratio (DR) meet the equation DR&gt;0.5+0.125×log Mw. These ethylene copolymers are different from a usual HDPE, L-LDPE and LDPE, and they are characterized in that working properties are excellent, and physical properties such as density, melting point and crystallinity can be controlled.

TECHNICAL FIELD

The present invention relates to a novel ethylene copolymer, athermoplastic resin composition containing the same, and a novel processfor preparing the ethylene copolymer. More specifically, the presentinvention relates to an ethylene copolymer which can be derived fromethylene and an olefin having 3 to 20 carbon atoms and in which thecontrol of the activation energy of melt flow is possible and physicalproperties such as density, a melting point and crystallinity can becontrolled; a thermoplastic resin composition containing this ethylenecopolymer; and a process for efficiently preparing the ethylenecopolymer in which non-Newtonian properties are improved and which isexcellent in working properties.

BACKGROUND ART

Heretofore, with regard to a polyethylene or an ethylene-α-olefincopolymer, its primary structure has been controlled by adjustingmolecular weight, a molecular weight distribution or copolymerizationproperties (random properties, a blocking tendency and a branchingdegree distribution), or by adding a third component such as a diene soas to introduce branches.

On the other hand, for ethylenic polymers, various molding methods areusable, and typical known examples of the molding methods includeinjection molding, extrusion, blow molding, inflation, compressionmolding and vacuum forming. In such molding methods, the impartment ofhigh-speed molding properties and the reduction of molding energy havebeen investigated for a long period of time in order to improve workingproperties and to thus lower a working cost, and so it is an importanttheme that optimum physical properties suitable for each use is impartedand the molding can be carried out with the optimum working properties.

In recent years, it has been elucidated that a uniform metallocenecatalyst is excellent in the copolymerization properties betweenolefins, can obtain a polymer having a narrow molecular weightdistribution, and has a much higher catalytic activity as compared witha conventional vanadium catalyst. Therefore, it has been expected thatthe metallocene catalyst will be developed in various technical fieldsby the utilization of such characteristics. However, a polyolefinobtained by the use of the metallocene catalyst is poor in molding andworking properties, and for this reason, the application of themetallocene catalyst to the blow molding and the inflation isunavoidably limited.

A conventional known low-density polyethylene (LDPE) can be obtained bythe high-pressure radical polymerization of ethylene and has both oflong-chain branches and short-chain branches. It has been consideredthat the long-chain branches can be formed by the intermolecularhydrogen transfer reaction between the radical growth terminal of thepolymer and the polymer. On the other hand, with regard to the mechanismfor forming the short-chain branches, some theories have been reported.For example, a back-biting mechanism has been suggested J. Am. Chem.Soc., Vol. 75, p. 6110 (1953)!. This suggested theory rationallyexplains that the butyl branch can be formed by the transfer of hydrogenafter the formation of a six-membered intermediate at the growth radicalterminal. According to another theory, it has been reported that thebutyl branch is formed by the production of an associate of two ethylenemolecules under a high pressure and a hydrogen transfer reaction at theradical growth terminal, and an ethyl branch can be introduced owing tothe production of 1-butene by the hydrogen transfer reaction in theassociate of two ethylene molecules Makromol. Chem. Vol. 181, p. 2811(1981)!. According to still another theory, it has been reported thatthe formation of the ethyl branch is accomplished by the transfer ofhydrogen from the main chain of the polymer to an ethyl branch radicalJ. Polym. Sci., Vol. 34, p. 569 (1959)!.

As understood from the foregoing, it can be summarized that theformation of the long-chain branches and the short-chain branches in thelow-density polyethylene is carried out by (1) the hydrogen transferreaction based on a radical polymerization and (2) the change of radicalpolymerization reactivity by the association of ethylene molecules undera high pressure, and this is a usually recognized reaction mechanism.Therefore, in the above-mentioned reaction process, it is impossible tooptionally control the amounts of the existing long-chain branches andshort-chain branches as well as the number of carbon atoms in theshort-chain branches. In particular, there have been limited theintroduction and control of a methyl branch, a propyl branch, a hexylbranch and a short-chain branch derived from a branched α-olefin (e.g.,a 4-methylpentene-1 branch).

Such a low-density polyethylene has a large melt tension and the largeactivation energy of melt flow by virtue of the long-chain branches, andtherefore it is excellent in high-speed molding properties and suitablefor the formation of films. However, since having a wide molecularweight distribution and containing a low-molecular weight component, thelow-density polyethylene is inconveniently poor in environmental stresscrack resistance (ESCR) and impact resistance.

On the other hand, various ethylenic polymers have been disclosed inwhich the long-chain branches are introduced into a high-densitypolyethylene skeleton. For example, there have been disclosed (1) anolefin copolymer having the long-chain branches obtained by the use ofan α,ω-diene or a cyclic endomethylenic diene (Japanese PatentApplication Laid-open No. 34981/1972), (2) a process for preparing acopolymer containing a higher non-conjugated diene content in ahigh-molecular weight segment than in a low-molecular weight segmentwhich comprises carrying out polymerization in two steps to copolymerizethe non-conjugated diene with an olefin (Japanese Patent ApplicationLaid-open No. 56412/1984), (3) an ethylene-α-olefin-1,5-hexadienecopolymer obtained by the use of a metallocene/aluminoxane catalyst(Japanese Patent Application PCT-through Laid-open No. 501555/1989), (4)a process for introducing the long-chain branches by copolymerizing anα,ω-diene and ethylene in the presence of a catalyst comprising azero-valent or a divalent nickel compound and a specific aminobis(imino)compound (Japanese Patent Application Laid-open No. 261809/1990), and(5) a polyethylene containing both of the short-chain branches and thelong-chain branches which can be obtained by polymerizing ethylene aloneby the use of the same catalytic component as in the above-mentioned (4)(Japanese Patent Application Laid-open No. 277610/1991).

However, in the copolymer of the above-mentioned (1), a crosslinkingreaction takes place simultaneously with the formation of the long-chainbranches by the diene component, and at the time of the formation of afilm, a gel is generated. In addition, melt properties inverselydeteriorate, and a control range is extremely narrow. Moreover, there isa problem that copolymerization reactivity is low, so that low-molecularweight polymers are produced, which leads to the deterioration ofphysical properties inconveniently. In the preparation process of thecopolymer described in the aforesaid (2), the long-chain branches areintroduced into the high-molecular weight component, so that themolecular weight noticeably increases due to crosslinking, and thusinsolubilization, nonfusion or gelation might inconveniently occur.Furthermore, the control range is narrow, and the copolymerizationreactivity is also low, and hence, there is a problem that owing to theproduction of the low-molecular weight polymers, the physical propertiesdeteriorate inconveniently. In the copolymer of the above-mentioned (3),a molecular weight distribution is narrow, and for this reason, thecopolymer is unsuitable for blow molding and film formation. Inaddition, since branch points are formed by the progress of thecyclizing reaction of 1,5-hexadiene, an effective monomer concentrationis inconveniently low. In the process for introducing the long-chainbranches described in the above-mentioned (4), there is a problem that arange for controlling the generation of a gel and the physicalproperties is limited. In addition, the polyethylene of theabove-mentioned (5) is a polymer which contains neither ethyl branchesnor butyl branches, and therefore the control of the physicalproperties, for example, the control of density is accomplished bymethyl branches, so that the physical properties of the polyethylenetend to deteriorate.

Furthermore, there has been disclosed a method for preparing anethylenic polymer to which working properties are imparted by theutilization of copolymerization, for example, a method which comprisesforming a polymer ( η!=10-20 dl/g) by preliminary polymerization, andthen preparing an ethylene-α-olefin copolymer by main polymerization(Japanese Patent Application Laid-open No. 55410/1992). This method hasan effect that melt tension can be increased by changing the meltproperties of the obtained copolymer, but it has a drawback that a filmgel tends to occur.

In addition, there have been disclosed ethylenic polymers obtained inthe presence of a metallocene catalyst and methods for preparing thesame, for example, (1) a method for preparing an ethylenic polymer inthe presence of a restricted geometrical catalyst and an ethyleniccopolymer obtained by this method (Japanese Patent Application Laid-openNo. 163088/1991 and WO93/08221), (2) a method for preparing a polyolefinin the presence of a metallocene catalyst containing a porous inorganicoxide (an aluminum compound) as a carrier (Japanese Patent ApplicationLaid-open No. 100808/1992), and (3) an ethylene-α-olefin copolymer whichcan be derived from ethylene and the α-olefin in the presence of aspecific hafnium catalyst and which has a narrow molecular weightdistribution and improved melt flow properties (Japanese PatentApplication Laid-open No. 276807/1990).

However, in the technique of the above-mentioned (1), the control ofdensity and the like can be accomplished by introducing an α-olefin unitinto an ethylene chain, and the resultant product is a substantiallylinear polymer. According to the preparation method of theabove-mentioned (2), the obtained copolymer of ethylene and the α-olefinhas a large die swell ratio, but in view of the relation of the dieswell ratio to the melting point of the ethylene-1-butene copolymer, itis apparent that the die swell ratio deteriorates with the rise of themelting point. Therefore, any copolymer cannot be provided in which thedie swell ratio regarding a neck-in which is a trouble at the time ofthe formation of a film or a sheet is controllable in a wide meltingpoint range.

On the other hand, the copolymer disclosed in the above-mentioned (3)contains an α-olefin unit as an essential unit, and it does not coverany copolymer having a resin density of more than 0.92 g/cm³.Additionally in its examples, copolymers having resin densities of 0.89g/cm³ or less are only disclosed. Furthermore, in the above-mentioned(1) and (3), when the branches are introduced, the melting point and themechanical strength of the ethylene-α-olefin copolymer noticeablydeteriorate.

DISCLOSURE OF THE INVENTION

Under such circumstances, the present invention has been intended. Anobject of the present invention is to provide a novel ethylene copolymerwhich can control the activation energy of melt flow, is excellent inworking properties, can control physical properties such as density, amelting point and crystallinity mainly, has a higher melting point ascompared under conditions of the same density, and is different from ausual high-density polyethylene (HDPE) as well as an ethylene-α-olefincopolymers and a low-density polyethylene (LDPE) disclosed in theabove-mentioned Japanese Patent Application Laid-open No. 163088/1991,WO93/08221 and Japanese Patent Application Laid-open No. 276809/1990.

The present inventors have intensively researched to achieve theabove-mentioned object, and as a result, it has been found that acopolymer derived from ethylene and an olefin having 3 to 20 carbonatoms is fit for the accomplishment of the object. That is to say, thiskind of copolymer has a polymeric main chain containing no quaternarycarbon and the activation energy (Ea) of melt flow in a specific range.Furthermore, in the copolymer of the present invention, (1) Hugginscoefficients of the copolymer and a straight-chain ethylene polymerhaving the same intrinsic viscosity stand in a specific relation to eachother; (2) a molar ratio CH₃ /CH₂ ! of a methyl group and a methylenegroup present in its molecular chain is within a specific range, andthis molar ratio and a melting point (Tm) meet a specific relativeequation; or (3) a weight-average molecular weight (Mw) and a die swellratio (DR) meet a specific relative equation. In addition, it has beenfound that when a specific catalyst for polymerization is used, theactivation energy of melt flow and the Huggins coefficient can becontrolled to effectively obtain the ethylene copolymer having improvednon-Newtonian properties and excellent working properties. Inconsequence, the present invention has been completed on the basis ofsuch a knowledge.

That is to say, according to the present invention, there can beprovided:

(1) An ethylene copolymer 1! which is derived from ethylene and anolefin having 3 to 20 carbon atoms and in which (1) any quaternarycarbon atom is not present in a polymeric main chain; (2) the activationenergy (Ea) of melt flow is in the range of 8 to 20 kcal/mol; and (3) aratio between Huggins coefficients (k) of the copolymer and astraight-chain ethylene polymer having the same intrinsic viscosity η!measured at a temperature of 135° C. in a decahydronaphthalene(hereinafter decalin) solvent meets the relation of the equation

    1.12<k.sup.1 /k.sup.2 ≦5

wherein k¹ is the Huggins coefficient of the copolymer, and k² is theHuggins coefficient of the straight-chain ethylene polymer.

(2) An ethylene copolymer 2! which is derived from ethylene and anolefin having 3 to 20 carbon atoms and in which (1) any quaternarycarbon atom is not present in a polymeric main chain; (2) the activationenergy (Ea) of melt flow is in the range of 8 to 20 kcal/mol; and (3) amolar ratio CH₃ /CH₂ ! of a methyl group in a region of 0.8 to 1.0 ppmto a methylene group in a region of 1.2 to 1.4 ppm observed by a protonnuclear magnetic resonance spectrum method (¹ H-NMR) is in the range of0.005 to 0.1, and a melting point (Tm) and the molar ratio CH₃ /CH₂ !observed by a differential scanning calorimeter (DSC) meet the equation

    Tm≧131-1,340  CH.sub.3 /CH.sub.2 !.

(3) An ethylene copolymer 3! which is derived from ethylene and anolefin having 3 to 20 carbon atoms and in which (1) any quaternarycarbon atom is not present in a polymeric main chain; (2) the activationenergy (Ea) of melt flow is in the range of 8 to 20 kcal/mol; and (3)the relation between a weight-average molecular weight (Mw) in terms ofthe polyethylene measured by a gel permeation chromatography method anda die swell ratio (DR) meet the equation

    DR>0.5+0.125×log Mw.

Moreover, according to the present invention, there can be provided anethylene copolymer obtained by subjecting any one of the above-mentionedethylene copolymers to a hydrogenation treatment, and a thermoplasticresin composition comprising any one of these ethylene copolymers.

In addition, according to the present invention, there can be provided aprocess for preparing an ethylene copolymer which comprises the step ofcopolymerizing ethylene and at least one selected from olefins having 3to 20 carbon atoms in the presence of a catalyst comprising (a) atransition metal compound in which the relation between a monomer chargecomposition a molar ratio M! of 1-octene/(ethylene+1-octene)! and theproduct of a crystallization enthalpy (ΔH) and a melting point (Tm) ofthe produced copolymer meets the equation

    0≦ΔH·Tm≦27,000-21,600  M!.sup.0.56

(under polymerization conditions using the component (a) together withan aluminoxane), (b) a transition metal compound capable of forming aterminal vinyl group in the homopolymerization of ethylene or thecopolymerization of ethylene and at least one selected from olefinshaving 3 to 20 carbon atoms (under polymerization conditions using thecomponent (b) together with the aluminoxane), and (c) a compound capableof forming an ionic complex from the above-mentioned components (a) and(b) or their derivatives (the transition metal compounds of theabove-mentioned components (a) and (b) are compounds containing metalsin the groups 3 to 10 or a lanthanide series of the periodic table).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph for judging whether or not a polymer concentration anda reduced viscosity stand in a linear relation to each other.

FIG. 2 shows a ¹³ C-NMR spectrum of the ethylene-1-butene coplolymerobtained in Example 1.

FIG. 3 is a graph showing the shear rate dependence of the meltviscosity of an ethylene copolymer obtained in Example 14 andComparative Example 3.

BEST MODE FOR CARRYING OUT THE INVENTION

An ethylene copolymer of the present invention is different from a usualHDPE, L-LDPE (a linear low-density polyethylene) and LDPE (ahigh-pressure method), and some differences can be judged by (A) theevaluation of a primary structure and (B) the evaluation of physicalproperties which will be described hereinafter.

(A) Judgment by evaluation of primary structure

(1) Comparison with HDPE, L-LDPE and LDPE

According to the measurement of ¹³ C-nuclear magnetic resonance spectra,it is apparent that the ethylene copolymer of the present invention isdifferent from the HDPE, L-LDPE and LDPE in structure.

(a) Comparison with HDPE (a relatively low-molecular weight polymer)

The terminal structure of a usual HDPE (a relatively low-molecularweight polymer) is represented by ##STR1##

A=13.99, B=22.84, C=30.00, and D=32.18 (unit=ppm)

(A, B and D are minute peaks) and any peak based on a branch is notpresent.

(b) Comparison with ethylene-α-olefin copolymers

(Ethylene-1-butene copolymer)

The ethylene-1-butene copolymer has a structure represented by ##STR2##

A=11.14, B=26.75, C=27.35, D=30.00, E=30.49, F=34.11, and G=39.75(unit=ppm)

as a structure in the vicinity of a branch point.

(Ethylene-1-hexene copolymer)

The ethylene-1-butene copolymer has a structure represented by ##STR3##

A=14.08, B=23.36, C=27.33, D=29.57, E=30.00, F=30.51, G=34.22, H=34.61,and I: 38.23 (unit=ppm)

as a structure in the vicinity of the branch point.

(Ethylene-4-methylpentene-1 copolymer)

The ethylene-4-methylpentene-1 copolymer has a structure represented by##STR4##

A=23.27, B=26.05, C=27.14, D=30.00, E=30.51, F=34.88, G=36.03, andH=44.83 (unit=ppm)

as a structure in the vicinity of the branch point.

(Ethylene-1-octene copolymer)

The ethylene-1-octene copolymer has a structure represented by ##STR5##

A=14.02, B=22.88, C=27.28, D=27.33, E=30.00, F=30.51, G=32.20, H=34.59,and I=38.25 (unit=ppm)

as a structure in the vicinity of the branch point.

(Ethylene-propylene copolymer)

The ethylene-propylene copolymer has a structure represented by ##STR6##

A=19.98, B=27.47, C=30.00, D=33.31, and E=37.59 (unit=ppm)

as a structure in the vicinity of the branch point.

In each of the above-mentioned ethylene-α-olefin copolymers, ashort-chain branch derived from the α-olefin is present, but anylong-chain branch is not present.

(c) Comparison with LDPE

The ¹³ C-NMR spectrum of the LDPE is complex, and it indicates thatshort-chain branches (ethyl and butyl branches) and long-chain branches(at least a hexyl branch and the like) are present in the LDPE.Furthermore, the LDPE is considered to mainly have the followingstructures (c-1) to (c-5) in the vicinity of the branches.

(c-1) Isolated branch (Bn) ##STR7##

xBn! (n=1, 2, 3 . . . , n)

(x=1, 2, 3 . . . , n, α, β, γ . . . )

(c-2) Ethyl-ethyl (1,3) branch bonded to a quaternary carbon (peq)##STR8##

(xB₂)_(peq), (xB'₂)_(peq) !

(c-3) Isolated ethyl-ethyl (1,3) branch (pee) ##STR9##

(xB₂)_(pee) !

(c-4) Isolated ethyl-propyl (1,3) branch (pep) ##STR10##

(xB₂)_(pep), (xB₃)_(pep) !

(c-5) Isolated methyl-ethyl (1,4) branch (pme) ##STR11##

(xB₂)_(pme), (xB₁)_(pme) !

The LDPE is considered to mainly have the structures of theabove-mentioned (c-1) to (c-5), and these structures have beenidentified Macromolecules, Vol. 17, p. 1756 (1984)!.

According to this literature, the identification has been made as shownin FIG. 1, and the presence of the long-chain branch (32.18 ppm) of atleast a hexyl branch and an ethyl branch has been confirmed.

                  TABLE 1                                                         ______________________________________                                              Chemical                 Chemical                                       No.   Shift    Assignment                                                                              No.   Shift   Assignment                             ______________________________________                                        1     42.86              15    24.36   β-CH.sub.2                        2     39.75    brB.sub.2               (bonded to                                                                    carbonyl                                                                      group)                                 3     39.19              16    23.36   2B.sub.4                               4     38.23    brB.sub.4-n                                                                             17    22.88   2B.sub.4                               5     37.38    (brB.sub.2).sub.pee                                                                           22.84   2B.sub.6-n                             6     35.99              18    20.15   2B.sub.3                               7     35.00                    20.04   1B.sub.1                               8     34.61    αB.sub.4-n                                                                        19    14.59   1B.sub.3                               9     34.22    4B.sub.4  20    14.08   1B.sub.4                               10    32.70    3B.sub.5        14.02   1B.sub.5-n                             11    32.18    3B.sub.n  21    11.22                                          12    30.00    CH.sub.2        11.01   1B.sub.2 or                                           Main Chain              (1B.sub.2).sub.pee                     13    27.33    βB.sub.4-n 10.85                                          14    25.99    βB'.sub.2                                                                          22     8.15                                                                          7.87   1B'.sub.2                              ______________________________________                                    

(2) Trial of presence confirmation of long-chain branch by ¹³ C-nuclearmagnetic resonance spectrum

There has been suggested a technique which confirms the presence of thehexyl branch and determines the hexyl branch by comparison with anethylene-1-octene copolymer having the hexyl branch Macromolecules, Vol.14, p. 215 (1981), and the same, Vol. 17, p. 1756 (1984)!. According tothese magazines, it has been elucidated from the measurement of the ¹³C-nuclear magnetic resonance spectrum of a blend with the LDPE that apeak observed at about 27.3 ppm is different from a peak observed in thecase of the ethylene-1-octene copolymer. Furthermore, in normal C₃₆ H₇₄which is used as a model substance of the long-chain branch, the thirdcarbon signal from its terminal appears at 32.18 ppm. On the other hand,the third carbon signal from the terminal of the hexyl branch of theethylene-1-octene copolymer appears at 32.22 ppm. In order to utilize afact that the presence of the long-chain branch has an influence on achemical shift, when the ethylene-1-octene copolymer is blended with theLDPE having the long-chain branch and a ¹³ C-nuclear magnetic resonancespectrum is then measured, two peaks appear, whereby the long-chainbranch of the LDPE can be identified and determined.

By such techniques, it can be confirmed that the LDPE has the long-chainbranch.

(B) Judgment by evaluation of physical properties

(1) Judgment by analysis of melt

It is known that the long-chain branch is concerned with the fluidbehavior of a melt viscosity, viscoelastic properties and the like of amelt, and it has a serious influence on mechanical properties such asworkability, optical properties and environmental stress-crackresistance of a resin. Therefore, by measuring and evaluating them, thepresence of the long-chain branch can be indirectly confirmed.

Furthermore, as reasons for supporting the presence of the long-chainbranch, there are the following facts. The relation between the MI andthe Mw of the LDPE deviates from the relation in the case of astraight-chain polyethylene (HDPE), as the number of the long-chainbranches increases. That is to say, the LDPE shows the smaller MI oncondition that the Mw is the same. In addition, by an Instron typecapillary rheometer, the fluid characteristics can be inspected, and ashift factor can be then utilized to determine the activation energy(Ea) of melt flow. Such a measured activation energy (Ea) of the HDPE isas small as 6 kcal/mol, and on the other hand, the Ea of the LDPE is aslarge as about 12 kcal/mol. In consequence, it can be confirmed that thefluid characteristics are affected by the long-chain branches.

According to such an analysis of the melt flow, it has been stronglyimplied that the ethylene copolymer of the present invention has longchains.

(2) Discrimination by analysis of polymer solution

(a) Judgment by Huggins coefficient

It is known that among a reduced viscosity η_(sp) /c (dl/g), anintrinsic viscosity η! (dl/g), a Huggins coefficient k and a polymerconcentration c (g/dl), the relation of the general equation (a Huggins'equation)

    η.sub.sp /c= η!+k η!.sup.2 c

can be established. The Huggins coefficient k is a value which denotesthe intermolecular interaction of a polymer in a dilute solution state,and so this coefficient k is considered to be affected by the molecularweight of the polymer, a molecular weight distribution and the presenceof the branch.

It has been elucidated that when the branch is introduced into a polymerstructure, the Huggins coefficient increases in the case of astyrene-divinylbenzene copolymer J. Polymer Sci., Vol. 9, p. 265(1952)!. Furthermore, it has also been disclosed that the Hugginscoefficient of the LDPE having the long-chain branch is larger than thatof the straight-chain HDPE Polymer Handbook, published by John WileySons, (1975)!.

(b) Judgment by relation between intrinsic viscosity η! and molecularweight measured by gel permeation chromatography method orlight-scattering method

It is known that the relation between the intrinsic viscosity η!determined in a dilute polyethylene solution by the use of theabove-mentioned Huggins' equation and the molecular weight measured bythe gel permeation chromatography (GPC) method for determining themolecular weight in accordance with the size of a solute polymer or thelight-scattering method can reflect the branch structure of the polymer.For example, the straight-chain HDPE is different from the LDPE havingthe long-chain branch in the relation between the intrinsic viscosityand the molecular weight measured by the GPC method, and it has beenelucidated that when comparison is made on the condition that theintrinsic viscosity is constant, the molecular weight of the LDPE issmaller than that of the HDPE.

Next, reference will be made to characteristics of the ethylenecopolymer 1! to 3! of the present invention.

In each of the ethylene copolymers 1! to 3! of the present invention, itis necessary that any quaternary carbon atom should not be present in apolymeric main chain and the activation energy (Ea) of melt flow shouldbe in the range of 8 to 20 kcal/mol, preferably 8.5 to 19 kcal/mol, morepreferably 9 to 18 kcal/mol. If the activation energy (Ea) of melt flowis less than 8 kcal/mol, sufficient working properties cannot beobtained. Here, the activation energy (Ea) of melt flow is a valueobtained in the following manner. First, frequency dependences (10⁻² to10² rad/sec) of dynamic viscoelastic properties are measured attemperatures of 150° C., 170° C., 190° C., 210° C. and 230° C., and theactivation energy (Ea) is then calculated on the basis of the shiftfactors of G', G" at the respective temperatures and the reciprocalnumber of an absolute temperature in accordance with the Arrhenius'equation by the use of a temperature-time conversion rule at a standardtemperature of 170° C.

Furthermore, the ethylene copolymers 1! to 3! of the present inventioncan meet the above-mentioned requirements and have the followingcharacteristics.

In the first place, the ethylene copolymer 1! can be specified by thefollowing ratio between Huggins coefficients (k) which are decided bythe relation between a polymer concentration and a reduced viscositymeasured at a temperature of 135° C. in a decalin solvent. That is tosay, if the straight-chain ethylene copolymer and the ethylene copolymer1! of the present invention have the same intrinsic viscosity η!measured at a temperature of 135° C. in the decalin solvent, theethylene copolymer 1! meets the ratio between the Huggins coefficients(k) represented by the equation

    1.12<k.sup.1 /k.sup.2 ≦5

wherein k¹ is a Huggins coefficient of the ethylene copolymer 1! of thepresent invention, and k² is a Huggins coefficient of the straight-chainethylene copolymer.

This ratio k¹ /k² meets a relation of, preferably

    1.13≦k.sup.1 /k.sup.2 ≦4.0

more preferably

    1.14≦k.sup.1 /k.sup.2 ≦3.7

further preferably

    1.15≦k.sup.1 /k.sup.2 ≦3.6

most preferably

    1.18≦k.sup.1 /k.sup.2 ≦3.4.

A typical example of the straight-chain ethylene copolyme referred toherein is an ethylene polymer presently produced on an industrial scaleor an ethylene polymer produced on a laboratory scale.

The preparation process uses a usual Ziegler catalyst, for example, acatalyst mainly comprising a combination of a transition metal compoundsuch as a titanium compound, a zirconium compound, a hafnium compound ora chromium compound and an organic metallic compound such astriethylaluminum or tributylaluminum, above all, an organic aluminumcompound. Furthermore, the above-mentioned catalyst in which a magnesiumcompound or a silicon compound is used as a carrier is also usable inthe preparation process. The intrinsic viscosity 1! can be controlled bythe use of hydrogen, a polymerization temperature, the amount of themonomer to be charged, the amount of the catalyst, and the like.

Assuming that the Huggins coefficient of the straight-chainethylene/α-olefin copolymer, which is obtained by a Ziegler catalyst andin which an intrinsic viscosity η! measured at a temperature of 135° C.in the decalin solvent is the same as in the ethylene copolymer 1! ofthe present invention, is represented by k³, the ratio k¹ /k³ of theHuggins coefficient k¹ of the ethylene copolymer 1! of the presentinvention to the above-mentioned k³ meets a relation of, usually

    1.02<k.sup.1 /k.sup.3 ≦5.0

preferably

    1.03≦k.sup.1 /k.sup.2 ≦4

more preferably

    1.05≦k.sup.1 /k.sup.2 ≦3.5.

Also in this point, the ethylene copolymer 1! of the present inventionis different from the conventional ethylene/α-olefin copolymer.

Furthermore, an α-olefin moeity or an α-olefin copolymer composition inthe above-mentioned straight-chain ethylene/α-olefin copolymer which canbe used for comparison has a relatively small influence on the Hugginscoefficient, but it is desirable to make the comparison by the use ofthe same kind of α-olefin and the same resin density.

The intrinsic viscosity η! and the Huggins coefficient k in theabove-mentioned relation equations can be obtained as follows.

That is to say, it is known that among the reduced viscosity ηsp/c(dl/g), the intrinsic viscosity η! (dl/g), the Huggins coefficient k andthe polymer concentration c (g/dl), the relation of the Huggins'equation

    η.sub.sp /c= η!+k η!.sup.2 c

can be established. In the first place, the reduced viscosity ηsp/c ismeasured in the decalin solvent at a polymer concentration of 2.0 g/dlor less at a measuring temperature of 135° C.±0.01° C. at 5 or moremeasuring points at an interval of a substantially constant polymerconcentration by the use of a Ubbelohde's viscometer. A measurementaccuracy is such that a relative viscosity is 1.1 or more and an errorof the relative viscosity is ±0.04% or less at each measuring point, andthe measurement is carried out 5 times or more every polymerconcentration. Furthermore, it is necessary that the polymerconcentration at the measuring point on the side of the lowestconcentration should be 45% or less of the polymer concentration at themeasuring point on the side of the highest concentration.

The above-mentioned method can decide the Huggins coefficient only whenthe relation between the reduced viscosity and the polymer concentrationdefinitely is in a linear relation. When the polymer concentration ishigh or the molecular weight of the polymer is large, the linearrelation is not obtained, and therefore it is necessary that after thedecrease in the polymer concentration, the measurement should be madeagain. However, if the polymer concentration is extremely low, a regionin which the reduced viscosity does not depend upon the polymerconcentration and a region in which the reduced viscosity increases withthe decrease in the polymer concentration might be present, and in theseregions, the Huggins coefficient cannot be calculated.

Moreover, if the measuring point is present apparently below a straightline depicted by connecting a measuring point (C_(n)) at the highestconcentration to a measuring point (C₁) at the lowest concentration, inthis region, the Huggins coefficient cannot be calculated. However, thisdoes not apply, as far as the following conditions are met. That is tosay, it can be judged in the following manner whether or not the linearrelation is established. In FIG. 1, the measuring point (C_(n)) at thehighest concentration is first connected to the measuring point (C₁) atthe lowest concentration with a straight line. Then, the respectivemeasuring points are connected to each other with a smooth curve. Here,a most separate distance between the straight line and the curve (η_(sp) /c!^(H) - η_(sp) /c!^(L)) is calculated, and if ( η_(sp)/c!^(H) - η_(sp) /c!^(L))/ C_(n) -C₁ ! is 0.001 or less, it can bejudged that the linear relation is established.

This ethylene copolymer 1! is dissolved in decalin at a temperature of135° C. The copolymer usually is neither indissoluble nor infusible in abroad density range, and hence any gel is not contained, so that theethylene copolymer 1! is dissolved in decalin at a temperature of 135°C. Furthermore, the ethylene copolymer 1! exerts a good solubility inaromatic hydrocarbons (tetrachlorobenzene and the like) and high-boilinghydrocarbons other than decalin, usually when heated. In the LDPEobtained by high-pressure radical polymerization, the formation of thegel is partially observed in view of its production mechanism.

Furthermore, the melting point (Tm) of the ethylene copolymer 1! whichcan be observed by a differential scanning calorimeter (DSC) is usuallyin the range of 50° to 137° C., preferably 55° to 136° C., morepreferably 58° to 135° C., and the ethylene copolymer 1! also includesan ethylene-olefin copolymer which does not substantially show themelting point (Tm).

Moreover, the crystallization enthalpy (ΔH) of the ethylene copolymer 1!which can be observed by the DSC usually meets the equation

    0≦ΔH≦250.

Here, the crystallization enthalpy is a value obtained from anexothermic peak of crystallization observed at a time when a pressedsheet formed at a temperature of 190° C. by the use of the DSC (DSC7model, made by Perkin Elmer Co., Ltd.) is molten at a temperature of150° C. for 5 minutes and then cooled to -50° C. at a rate of 10°C./min. On the other hand, the melting point is a value obtained from atemperature at the maximum peak position of an endothermic peak offusion at the time of temperature rise at a rate of 10° C./min.

In the ethylene copolymer 2! of the present invention, a molar ratio CH₃/CH₂ ! of a methyl group in a region of 0.8 to 1.0 ppm to a methylenegroup in a region of 1.2 to 1.4 ppm obtained by a proton nuclearmagnetic resonance spectrum method (¹ H-NMR) is in the range of 0.005 to0.1, and it is necessary that the melting point (Tm) and CH₃ /CH₂ !observed by the differential scanning calorimeter (DSC) should meet theequation

    Tm≧131-1340  CH.sub.3 /CH.sub.2 !

preferably

    Tm≧131-1260  CH.sub.3 /CH.sub.2 !

more preferably

    Tm≧131-1190  CH.sub.3 /CH.sub.2 !

still more preferably

    Tm≧131-1120  CH.sub.3 /CH.sub.2 !.

Here, CH₃ /CH₂ ! can be decided by a known technique. That is to say, ifan integrated value of a peak present in a region of 0.8 to 1.0 ppm isregarded as A and an integrated value of a peak present in a region of1.2 to 1.4 ppm is regarded as B, CH₃ /CH₂ ! can be represented as A/3!/B/2!.

The melting point (Tm) is a value obtained from a temperature at themaximum peak position of an endothermic peak of fusion at a time whenthe pressed sheet formed at a temperature of 190° C. by the use of theDSC (DSC7 model, made by Perkin Elmer Co., Ltd.) is molten at atemperature of 150° C. for 5 minutes, cooled to -50° C. at a rate of 10°C./min, and then heated at a rate of 10° C./min.

In the ethylene copolymer 3! of the present invention, it is necessarythat a weight-average molecular weight (Mw) in terms of the polyethylenemeasured by gel permeation chromatography (GPC) and a die swell ratio(DR) meet the equation

    DR>0.5+0.125×log Mw,

preferably

    1.80>DR>0.36+0.159×log Mw,

more preferably

    1.75>DR>0.16+0.21×log Mw,

best preferably

    1.70>DR>-0.11+0.279×log Mw.

Here, the die swell ratio (DR) is a value (D₁ /D₀) obtained by measuringa diameter (D₁, mm) of a strand formed by extrusion through a capillarynozzle diameter (D₀)=1.275 mm, length (L)=51.03 mm, L/D₀ =40, andentrance angle=90°! at an extrusion speed of 1.5 mm/min (shear rate 10sec⁻¹) at a temperature of 190° C. by the use of a capillograph made byToyo Seiki Seisakusho Co., Ltd., and then dividing this diameter by thediameter of the capillary nozzle.

The above-mentioned diameter (D₁) of the strand is an average value ofvalues obtained by measuring long axes and short axes of centralportions of 5 samples having a extruded strand length of 5 cm (a lengthof 5 cm from a nozzle outlet).

The ethylene copolymers 1! to 3! of the present invention usually havethe following physical properties.

(1) A weight-average molecular weight (Mw) in terms of the polyethylenemeasured by the gel permeation chromatography (GPC) device=WatersALC/GPC 150C, column=made by Toso Co., Ltd., TSK HM+GMH6×2, flowrate=1.0 ml/min, and solvent=1,2,4-trichlorobenzene, 135° C.! is usuallyin the range of 5,000 to 2,000,000, preferably 7,000 to 1,500,000, morepreferably 10,000 to 1,000,000. If this weight-average molecular weight(Mw) is less than 5,000, the exertion of mechanical properties is poor,and if it is more than 2,000,000, working properties deteriorates.

(2) A ratio Mw/Mn of a weight-average molecular weight (Mw) to anumber-average molecular weight (Mn) in terms of the polyethylenemeasured by the GPC method is usually in the range of 1.5 to 70,preferably 1.6 to 60, more preferably 2.0 to 50.

(3) A resin density is usually in the range of 0.85 to 0.96 g/cm³,preferably 0.860 to 0.955 g/cm³, more preferably 0.870 to 0.950 g/cm³.This resin density is a value obtained by measuring, with a densitygradient tube, the pressed sheet formed at a temperature of 190° C. andthen quenched.

(4) The intrinsic viscosity η! measured in decalin at a temperature of135° C. is usually in the range of 0.01 to 20 dl/g, preferably 0.05 to17 dl/g, more preferably 0.1 to 15 dl/g. If this η! is less than 0.01dl/g, the exertion of the mechanical properties is poor, and if it ismore than 20 dl/g, the working properties deteriorates.

Furthermore, in the ethylene copolymers 1! to 3! of the presentinvention, an unsaturated group is present at the terminal of eachmolecule, and this unsaturated group can easily be identified anddetermined by measuring the infrared absorption spectra of the pressedsheet (thickness=100 to 500 μm) formed at a temperature of 190° C.

    ______________________________________                                        Kind of terminal unsaturated group                                                             Position of absorption (cm.sup.-1)                           ______________________________________                                        Vinylene group   963                                                          Vinylidene group 888                                                          Vinyl group      907                                                          ______________________________________                                    

In each ethylene copolymer, the production ratio of the terminal vinylgroup is usually 30 mol % or more, preferably 40 mol % or more, morepreferably 50 mol % or more with respect to the sum of theabove-mentioned unsaturated groups. In this connection, the amount ofthe terminal vinyl group can be calculated in accordance with theequation

    n=0.114A.sub.907 / d·t!

wherein n is the number of the terminal vinyl groups with respect to 100carbon atoms; A₉₀₇ is an absorbance at 907 cm⁻¹ ; d is a resin density(g/cm³); and t is the thickness of the film (mm).

In general, it is known that an interrelation is present between theamount of the unsaturated group at the terminal and the molecularweight, but particularly in the ethylene copolymer copolymer 1! of thepresent invention, a terminal vinyl type unsaturated group content (U)and a reciprocal number of the intrinsic viscosity η! measured indecalin at a temperature of 135° C. usually meet the equation

    0≦U≦15× η!.sup.-1

preferably

    0≦U≦14× η!.sup.-1

more preferably

    0≦U≦13× η!.sup.-1

most preferably

    0≦U≦12× η!.sup.-1

wherein U is the number of the terminal vinyl groups with respect to1000 carbon atoms.

Various functions such as adhesive properties, printability, coatingproperties, compatibility, moisture permeability and barrier properties,which are insufficient in a polyolefin, can be imparted to the ethylenecopolymers 1! to 3! having the high unsaturated group content at theterminal by the modification of the unsaturated group, andsimultaneously, the improvement of the working properties based on thebranch can be expected. In addition, the ethylene polymers having thehigh terminal vinyl group content can be used as a branched micromonomerfor the manufacture of various graft copolymers. On the other hand, inthe ethylene copolymers having a low terminal unsaturated group content,thermal stability can be improved, and the working properties based onthe branch can be expected. Functions such as the adhesive propertiesand the printability can be sufficiently exerted by a practicalmodification even in the case of the ethylene copolymers having the lowterminal unsaturated group content.

The present invention also provides an ethylene copolymer in which sucha carbon-carbon unsaturated bond is hydrogenated, and in the ethylenecopolymer in which the unsaturated groups are reduced or lost by thishydrogenation treatment, the thermal stability can be improved.

The ethylene copolymers (the unhydrogenated ethylene copolymers and thehydrogenated ethylene copolymers) of the present invention can each bemixed with another thermoplastic resin and then used as thermoplasticresins. Examples of the other thermoplastic resin include polyolefinresins, polystyrene resins, condensation series high-molecular weightpolymers and addition polymerization series high-molecular weightpolymers. Typical examples of the polyolefin resins include high-densitypolyethylenes, low-density polyethylenes, poly-3-methylbutene-1,poly-4-methylpentene-1, straight-chain low-density polyethylenesobtained by the use of 1-butene, 1-hexene, 1-octene, 4-methylpentene-1and 3-methylbutene-1 as comonomer components, ethylene-vinyl acetatecopolymers, saponified ethylene-vinyl acetate copolymers,ethylene-acrylic acid copolymers, ethylene-acrylic acid estercopolymers, ethylenic ionomers and polypropylene. Typical examples ofthe polystyrene resins include general-purpose polystyrenes, isotacticpolystyrenes and (rubber modified) high-impact polystyrenes. Typicalexamples of the condensation series high-molecular weight polymersinclude polyacetal resins, polycarbonate resins, polyamide resins suchas 6-nylon and 6,6-nylon, polyester resins such as polyethyleneterephthalates and polybutylene terephthalates, polyphenylene oxideresins, polyimide resins, polysulfone resins, polyethersulfone resinsand polyphenylene sulfide resins. Examples of the additionpolymerization series high-molecular weight polymers include polymersobtained from polar vinyl monomers and polymers obtained from dienemonomers, typically, polymethyl methacrylate, polyacrylonitrile,acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrenecopolymer, diene polymers in which a diene chain is hydrogenated, andthermoplastic elastomers.

A thermoplastic resin composition of the present invention can beobtained by blending 100 parts by weight of the above-mentioned ethylenecopolymer of the present invention with 2 to 500 parts by weight,preferably 3 to 300 parts by weight, more preferably 5 to 200 parts byweight of the other thermoplastic resin (or the thermoplasticelastomer).

The ethylene copolymer of the present invention can be obtained bycopolymerizing ethylene with an olefin having 3 to 20 carbon atoms, andthe olefin having 3 to 20 carbon atoms which can be as a comonomerinclude α-olefins, cyclic olefins and styrenes.

Examples of the α-olefins include propylene, 1-butene, 1-pentene,4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene,1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and3-methyl-1-butene.

Examples of the cyclic olefins include norbornene, 5-methylnorbornene,5-ethylnorbornene, 5-propylnorbornene, 5,6-dimethylnorbornene,1-methylnorbornene, 7-methylnorbornene, 5,5,6-trimethylnorbornene,5-phenylnorbornene, 5-benzylnorbornene, 5-ethylidenenorbornene,1,4,5,8-dimethanol-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-methyl-1,4,5,8-dimethanol-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-cyclohexyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2,3-dichloro-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-isobutyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,1,2-dihydrodicyclopentadiene, 5-chloronorbornene,5,5-dichloronorbornene, 5-fluoronorbornene,5,5,6-trifluoro-6-trifluoromethylnorbornene, 5-chloromethylnorbornene,5-methoxynorbornene, 5,6-dicarboxylnorbornene anhydride,5-dimethylaminonorbornene, 5-cyanonorbornene,2-ethyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2,3-dimethyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-hexyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-ethylidene-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphalene,2-fluoro-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene and1,5-dimethyl-1,4,5,8-dimethanol-1,2,3,4,4a,5,8,8a-octahydronaphalene.Above all, norbornene and its derivatives are particularly suitable.

Examples of the styrenes include styrene, α-methylstyrene,p-methylstyrene, o-methylstyrene, p-chlorostyrene, p-t-butylstyrene,p-phenylenestyrene and p-trimethylstyrene.

These comonomers may be used singly or in a combination of two or morethereof.

The (unhydrogenated) ethylene copolymers of the present invention can beeach prepared by polymerizing ethylene with an olefin having 3 to 20carbon atoms in the presence of such a polymerization catalyst as topermit the preparation of the ethylene copolymer having theabove-mentioned characteristics.

An example of such a polymerization catalyst contains, as maincomponents, (A) a transition metal compound and (B) a compound capableof forming an ionic complex from the transition metal compound or itsderivative.

As the transition metal compound of the component (A) in thepolymerization catalyst, there can be used a transition metal compoundcontaining a metal in the groups 3 to 10 of the periodic table or ametal of a lanthanide series. Preferable examples of the transitionmetal include titanium, zirconium, hafnium, vanadium, niobium andchromium.

Examples of such a transition metal compound includes various kinds ofcompounds, and in particular, compounds containing transition metals inthe groups 4, 5 and 6 can be suitably used. Particularly suitable arecompounds represented by the general formulae

    CpM.sup.1 R.sup.1.sub.a R.sup.2.sub.b R.sup.3.sub.c        (I)

    Cp.sub.2 M.sup.1 R.sup.1.sub.a R.sup.2.sub.b               (II)

    (Cp-A.sub.e -Cp)M.sup.1 R.sup.1.sub.a R.sup.2.sub.b        (III)

or the general formula

    M.sup.1 R.sup.1.sub.a R.sup.2.sub.b R.sup.3.sub.c R.sup.4.sub.d(IV)

and their derivatives.

In the above-mentioned general formulae (I) to (IV), M¹ represents atransition metal such as titanium, zirconium, hafnium, vanadium, niobiumand chromium, and Cp represents a cyclic unsaturated hydrocarbon groupor a chain unsaturated hydrocarbon group such as a cyclopentadienylgroup, a substituted cyclopentadienyl group, an indenyl group, asubstituted indenyl group, a tetrahydroindenyl group, a substitutedtetrahydroindenyl group, a fluorenyl group or a substituted fluorenylgroup. In this connection, a part of the carbon atoms in thecyclopentadienyl group may be substituted by a hetero-atom such asnitrogen or phosphorus. R¹, R², R³ and R⁴ each independently representsa σ-bond ligand, a chelate ligand or a ligand such as a Lewis base, andtypical examples of the σ-bond ligand include a hydrogen atom, an oxygenatom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, analkoxy group having 1 to 20 carbon atoms, an aryl group, an alkylarylgroup or an arylalkyl group having 6 to 20 carbon atoms, an acyloxygroup having 1 to 20 carbon atoms, an allyl group, a substituted allylgroup, and a substituent containing a silicon atom. In addition,examples of the chelate ligand include an acetylacetonato group and asubstituted acetylacetonato group. A represents a crosslinkage by acovalent bond. a, b, c and d each is independently an integer of 0 to 4,and e is an integer of 0 to 6. Two or more of R¹, R², R³ and R⁴ may bondto each other to form a ring. In the case that the above-mentioned Cphas a substituent, this substituent is preferably an alkyl group having1 to 20 carbon atoms. In the formulae (II) and (III), the two Cps may bethe same or different from each other.

Examples of the substituted cyclopentadienyl group in theabove-mentioned formulae (I) to (III) include a methylcyclopentadienylgroup, an ethylcyclopentadienyl group, an isopropylcyclopentadienylgroup, a 1,2-dimethylcyclopentadienyl group, atetramethylcyclopentadienyl group, a 1,3-dimethylcyclopentadienyl group,a 1,2,3-trimethylcyclopentadienyl group, a1,2,4-trimethylcyclopentadienyl group, a pentamethylcyclopentadienylgroup and a trimethylsilylcyclopentadienyl group. Furthermore, typicalexamples of R¹ to R⁴ in the above-mentioned formulae (I) to (IV) includea fluorine atom, a chlorine atom, a bromine atom and an iodine atom asthe halogen atoms; a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an octyl group and a 2-ethylhexylgroup as the alkyl groups having 1 to 20 carbon atoms; a methoxy group,an ethoxy group, a propoxy group, a butoxy group and a phenoxy group asthe alkoxy groups having 1 to 20 carbon atoms; a phenyl group, a tolylgroup, a xylyl group and a benzyl group as the aryl groups, thealkylaryl groups or the arylalkyl groups having 6 to 20 carbon atoms; aheptadecylcarbonyloxy group as the acyloxy group having 1 to 20 carbonatoms; a trimethylsilyl group and a (trimethylsilyl)methyl group as thesubstituent containing a silicon atom; and ethers such as dimethylether, diethyl ether and tetrahydrofuran, a thioether such astetrahydrothiophene, an ester such as ethyl benzoate, nitriles such asacetonitrile and benzonitrile, amines such as trimethylamine,triethylamine, tributylamine, N,N-dimethylaniline, pyridine,2,2'-bipyridine and phenanthroline, phosphines such as triethylphosphineand triphenylphosphine, chain unsaturated hydrocarbons such as ethylene,butadiene, 1-pentene, isoprene, pentadiene, 1-hexene and theirderivatives, and cyclic unsaturated hydrocarbons such as benzene,toluene, xylene, cycloheptatriene, cyclooctadiene, cyclooctatriene,cyclooctatetraene and their derivatives as the Lewis base. In addition,examples of the crosslinkage by the covalent bond of A in the formula(III) include a methylene crosslinkage, a dimethylmethylenecrosslinkage, an ethylene crosslinkage, a 1,1'-cyclohexylenecrosslinkage, a dimethylsilylene crosslinkage, a dimethylgermilenecrosslinkage and a dimethylstanilene crosslinkage.

Examples of the compound represented by the general formula (I) include(pentamethylcyclopentadienyl)trimethylzirconium,(pentamethylcyclopentadienyl)triphenylzirconium,(pentamethylcyclopentadienyl)tribenzylzirconium,(pentamethylcyclopentadienyl)trichlorozirconium,(pentamethylcyclopentadienyl)trimethoxyzirconium,(pentamethylcyclopentadienyl)triethoxyzirconium,(cyclopentadienyl)trimethylzirconium,(cyclopentadienyl)triphenylzirconium,(cyclopentadienyl)tribenzylzirconium,(cyclopentadienyl)trichlorozirconium,(cyclopentadienyl)trimethoxyzirconium,(cyclopentadienyl)triethoxyzirconium,(cyclopentadienyl)dimethyl(methoxy)zirconium,(methylcyclopentadienyl)trimethylzirconium,(methylcyclopentadienyl)triphenylzirconium,(methylcyclopentadienyl)tribenzylzirconium,(methylcyclopentadienyl)trichlorozirconium,(methylcyclopentadienyl)dimethyl(methoxy)zirconium,(dimethylcyclopentadienyl)trichlorozirconium,(trimethylcyclopentadienyl)trichlorozirconium,(trimethylcyclopentadienyl)trimethylzirconium,(tetramethylcyclopentadienyl)trichlorozirconium, and these compounds inwhich zirconium is replaced with titanium or hafnium.

Examples of the compound represented by the general formulae (II)include bis(cyclopentadienyl)dimethylzirconium,bis(cyclopentadienyl)diphenylzirconium,bis(cyclopentadienyl)diethylzirconium,bis(cyclopentadienyl)dibenzylzirconium,bis(cyclopentadienyl)dimethoxyzirconium,bis(cyclopentadienyl)dichlorozirconium,bis(cyclopentadienyl)dihydridozirconium,bis(cyclopentadienyl)monochloromonohydridozirconium,bis(methylcyclopentadienyl)dimethylzirconium,bis(methylcyclopentadienyl)dichlorozirconium,bis(methylcyclopentadienyl)dibenzylzirconium,bis(pentamethylcyclopentadienyl)dimethylzirconium,bis(pentamethylcyclopentadienyl)dichlorozirconium,bis(pentamethylcyclopentadienyl)dibenzylzirconium,bis(pentamethylcyclopentadienyl)chloromethylzirconium,bis(pentamethylcyclopentadienyl) hydridomethylzirconium,(cyclopentadienyl)(pentamethylcyclopentadienyl)dichlorozirconium, andthese compounds in which zirconium is replaced with titanium or hafnium.

Furthermore, examples of the compound represented by the general formula(III) include ethylenebis(indenyl)dimethylzirconium,ethylenebis(indenyl)dichlorozirconium,ethylenebis(tetrahydroindenyl)dimethylzirconium,ethylenebis(tetrahydroindenyl)dichlorozirconium,dimethylsilylenebis(cyloropentadienyl)dimethylzirconium,dimethylsilylenebis(cyloropentadienyl)dichlorozirconium,isopropylidene(cyloropentadienyl)(9-fluorenyl)dimethylzirconium,isopropylidene(cyloropentadienyl)(9-fluorenyl)dichlorozirconium,phenyl(methyl)methylene!(9-fluorenyl)(cycylopentadienyl)dimethylzirconium,diphenylmethylene(cyclopentadienyl)(9-fluorenyl)dimethylzirconium,ethylene(9-fluorenyl)(cyclopentadienyl)dimethylzirconium,cyclohexalidene(9-fluorenyl)(cyclopentadienyl)dimethylzirconium,cyclopentylidene(9-fluorenyl)(cyclopentadienyl)dimethylzirconium,cyclobutylidene(9-fluorenyl)(cyclopentadienyl)dimethylzirconium,dimethylsilylene(9-fluorenyl)(cyclopentadienyl)dimethylzirconium,dimethylsilylenebis(2,3,5-trimethylcyclopentadienyl)dichlorozirconium,dimethylsilylenebis(2,3,5-trimethylcyclopentadienyl)dimethylzirconium,dimethylsilylenebis(indenyl)dichlorozirconium,isopropylidenebis(cyclopentadienyl)dichlorozirconium and these compoundsin which zirconium is replaced with titanium or hafnium.

Moreover, examples of the compound represented by the general formula(IV) include tetramethylzirconium, tetrabenzylzirconium,tetramethoxyzirconium, tetraethoxyzirconium, tetrabutoxyzirconium,tetrachlorozirconium, tetrabromozirconium, butoxytrichlorozirconium,dibutoxydichlorozirconium, bis(2,5-di-t-butylphenoxy)dimethylzirconium,bis(2,5-di-t-butylphenoxy)dichlorozirconium, zirconiumbis(acetylacetonato), and these compounds in which zirconium is replacedwith titanium or hafnium.

Typical examples of the vanadium compound include vanadium trichloride,vanadyl trichloride, vanadium triacetylacetonate, vanadiumtetrachloride, vanadium tributoxide, vanadyl dichloride, vanadylbisacetylacetonate, vanadyl triacetylacetonate, dibenzenevanadium,dicyclopentadienylvanadium, dicyclopentadienylvanadium dichloride,cyclopentadienylvanadium dichloride anddicyclopentadienylmethylvanadium.

Next, typical examples of the chromium compound includetetramethylchromium, tetra(t-butoxy)chromium,bis(cyclopentadienyl)chromium,hydridotricarbonyl(cyclopentadienyl)chromium,hexacarbonyl(cyclopentadienyl)chromium, bis(benzene)chromium,tricarbonyltris(triphenyl phosphonate)chromium, tris(allyl)chromium,triphenyltris(tetrahydrofuran)chromium and chromiumtris(acetylacetonate).

Furthermore, as the component (A), there can suitably be used a group 4transition compound having, as the ligand, a multiple ligand compound inwhich in the above-mentioned general formula (III), two substituted orunsubstituted conjugated cyclopentadienyl groups (however, at least oneof which is a substituted cyclopentadienyl group) is bonded to eachother via an element selected from the group 14 of the periodic table.

An example of such a compound is a compound represented by the generalformula (V) ##STR12## or its derivative.

In the above-mentioned general formula (V), Y¹ represents a carbon atom,a silicon atom, a germanium atom or a tin atom, R⁵ _(t) --C₅ H_(4-t) andR⁵ _(u) --C₅ H_(4-u) each represents a substituted cyclopentadienylgroup, and t and u each are an integer of 1 to 4. Here, R⁵ s eachrepresents a hydrogen atom, a silyl group or a hydrocarbon group, andthey may be the same or different from each other. In at least either ofthe cyclopentadienyl groups, R⁵ is present on at least either of carbonatoms adjacent to the carbon atom bonded to Y¹. R⁶ represents a hydrogenatom, an alkyl group having 1 to 20 carbon atoms, or an aryl group, analkylaryl group or an arylalkyl group having 6 to 20 carbon atoms. M²represents a titanium atom, a zirconium atom or a hafnium atom, X¹represents a hydrogen atom, a halogen atom, an alkyl group having 1 to20 carbon atoms, an aryl group, an alkylaryl group or an arylalkyl grouphaving 6 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbonatoms. X¹ may be the same or different from each other, and similarly,R⁶ is may be the same or different from each other.

Moreover, examples of the substituted cyclopentadienyl group in thegeneral formula (V) include a methylcyclopentadienyl group, anethylcyclopentadienyl group, an isopropylcyclopentadienyl group, a1,2-dimethylcyclopentadienyl group, a 1,3-dimethylcyclopentadienylgroup, a 1,2,3-trimethylcyclopentadienyl group and a1,2,4-trimethylcyclopentadienyl group. Typical examples of X¹ include F,Cl, Br and I as the halogen atoms; a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, an octyl group anda 2-ethylhexyl group as the alkyl group having 1 to 20 carbon atoms; amethoxy group, an ethoxy group, a propoxy group, a butoxy group and aphenoxy group as the alkoxy groups having 1 to 20 carbon atoms; and aphenyl group, a tolyl group, a xylyl group and a benzyl group as thearyl group, the alkylaryl group or the arylalkyl group having 6 to 20carbon atoms. Typical examples of the R⁶ include a methyl group, anethyl group, a phenyl group, a tolyl group, a xylyl group and a benzylgroup.

Examples of the compound having the general formula (V) includedimethylsilylenebis(2,3,5-trimethylcyclopentadienyl)zirconiumdichloride, dimethylsilylenebis(2,3,5-trimethylcyclopentadienyl)titaniumdichloride anddimethylsilylenebis(2,3,5-trimethylcyclopentadienyl)hafnium dichloride.

In addition, the compound having the general formula (V) also includescompounds represented by the general formula (VI): ##STR13##

In the compound of the general formula (VI), Cp represents a cyclicunsaturated hydrocarbon group or a chain unsaturated hydrocarbon groupsuch as a cyclopentadienyl group, a substituted cyclopentadienyl group,an indenyl group, a substituted indenyl group, a tetrahydroindenylgroup, a substituted tetrahydroindenyl group, a fluorenyl group or asubstituted fluorenyl group. M³ represents a titanium atom, a zirconiumatom or a hafnium atom, X² represents a hydrogen atom, a halogen atom,an alkyl group having 1 to 20 carbon atoms, an aryl group, an alkylarylgroup or an arylalkyl group having 6 to 20 carbon atoms, or an alkoxygroup having 1 to 20 carbon atoms. Z represents SiR⁷ ₂, CR⁷ ₂, SiR⁷ ₂SiR⁷ ₂, CR⁷ ₂ CR⁷ ₂, CR⁷ ₂ CR⁷ ₂ CR⁷ ₂, CR⁷ ═CR⁷, CR⁷ ₂ SiR⁷ ₂ or GeR⁷₂, and Y² represents --N(R⁶)--, --O--, --S-- or --P(R⁶)--. Theabove-mentioned R⁷ is a group selected from the group consisting of ahydrogen atom, an alkyl group having 20 or less non-hydrogen atoms, anaryl group, a silyl group, a halogenated alkyl group, a halogenated arylgroup and a combination thereof, and R⁶ is an alkyl group having 1 to 10carbon atoms or an aryl group having 6 to 10 carbon atoms, or R⁶ mayform a condensed ring of one or more R⁷ s and 30 or less non-hydrogenatoms. Moreover, w represents 1 or 2.

Typical examples of the compound represented by the general formula (VI)include (tert-butylamido)(tetramethyl-η⁵-cyclopentadienyl)-1,2-ethanediylzirconium dichloride,(tert-butylamido)(tetramethyl-η⁵-cyclopentadienyl)-1,2-ethanediyltitanium dichloride,(methylamido)(tetramethyl-η⁵ -cyclopentadienyl)-1,2-ethanediylzirconiumdichloride, (methylamido)(tetramethyl-η⁵-cyclopentadienyl)-1,2-ethanediyltitanium dichloride,(ethylamido)(tetramethyl-η⁵ -cyclopentadienyl)-methylenetitaniumdichloride, (tertbutylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitanium dichloride,(tert-butylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanezirconium dibenzyl,(benzylamido)dimethyl(tetramethyl-η⁵ -cyclopentadienyl)silanetitaniumdichloride and (phenylphosphide)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanezirconium dibenzyl.

Furthermore, as the transition metal compound which is the component(A), there can also be used a reaction product of a transition metalcompound represented by the general formula (IV) in which at least twohalogen atoms, an alkoxy group, or the two halogen atoms and the alkoxygroup are bonded to a central metal and any one of diols represented bythe general formulae (VII) to (XII): ##STR14##

In the compounds represented by the general formulae (VII) to (XII), R⁹and R¹⁰ are each a hydrocarbon group having 1 to 20 carbon atoms, andthey may be the same of different from each other, Y³ is a hydrocarbongroup having 1 to 20 carbon atoms, or a group represented by ##STR15##wherein R¹⁵ is a hydrocarbon group having 1 to 6 carbon atoms. Examplesof the hydrocarbon group having 1 to 20 carbon atoms which isrepresented by R⁹, R¹⁰ and Y³ include methylene, ethylene, trimethylene,propylene, diphenylmethylene, ethylidene, n-propylidene, isopropylidene,n-butylidene and isobutylidene, and above all, methylene, ethylene,ethylidene, isopropylidene and isobutylidene are preferable. n is aninteger of 0 or more, and 0 or 1 is particularly preferable.

Furthermore, R¹¹, R¹², R¹³ and R¹⁴ are each a hydrocarbon group having 1to 20 carbon atoms, a hydroxyl group, a nitro group, a nitrile group, ahydrocarbyloxy group or a halogen atom, and they may be the same ordifferent from each other. Examples of the hydrocarbon group having 1 to20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, t-butyl, n-amyl, isoamyl, n-hexyl,n-heptyl, n-octyl, n-decyl and n-dodecyl; aryl groups such as phenyl andnaphthyl; cycloalkyl groups such as cyclohexyl and cyclopentyl; analkenyl group such as propenyl; and an aralkyl group such as benzyl, andabove all, the alkyl groups having 1 to 10 carbon atoms are preferable.y, y', y", y'", z, z', z" and z'" are each the number of substituentsbonded to an aromatic ring, and y, y', z and z' are each an integer of 0to 4, y" and z" are each an integer of 0 to 2, and y'" and z'" are eachan integer of 0 to 3.

One example of the reaction product of the transition metal compound andeach of the diols represented by the general formulae (VII) to (XII) isa compound represented by the general formula (XIII): ##STR16##

In the general formula (XIII), M¹ is as defined above, E¹ and E² areeach a hydrocarbon group having 1 to 20 carbon atoms, v and x are each 0or 1, and E¹ and E² form a crosslinking structure via Y⁴. E³ and E⁴ areeach a σ-bond ligand, a chelate ligand or a Lewis base, and they may bethe same or different from each other.

v' and x' are each an integer of 0 to 2 v'+x'=an integer of (the valenceof M¹ -2)!. Y⁴ is a hydrocarbon group having 1 to 20 carbon atoms, E⁵ E⁶Y⁵, an oxygen atom or a sulfur atom, and m is an integer of 0 to 4. E⁵and E⁶ are each a hydrocarbon group having 1 to 20 carbon atoms, and Y⁵is a carbon atom or a silicon atom.

Typical examples of the compound represented by the general formula(XIII) include ##STR17##

Furthermore, the compound of the general formula (XIII) also includes acompound represented by the general formula (XIV): ##STR18##

In the general formula (XIV), R¹⁶ s are each an alkyl group or an acylgroup having 1 to 20 carbon atoms, a cycloalkyl group having 6 to 20carbon atoms, or an aryl group, an alkylaryl group or an arylalkyl grouphaving 6 to 20 carbon atoms, and the respective R¹⁶ s may be the same ordifferent from each other. M⁴ is a metallic element in the group 3 or 4of the periodic table or in a lanthanide series, and z is an integer of2 to 20.

Typical examples represented by the general formula (XIV) include BuOZr(OBu)₂ O!₄ -Bu, EtO Zr(OEt)₂ O!₄ -Et, iPrO Zr(OiPr)₂ O!₄ -iPr, nPrOZr(OnPr)₂ O!₄ -nPr, BuO Zr(OBu)₂ O!₃ -Bu, BuO Zr(OBu)₂ O!₂ -Bu, andthese compounds in which zirconium is replaced with titanium or hafnium.In these formulae, Bu is a butyl group, Et is an ethyl group, nPr is anormal propyl group, and iPr is an isopropyl group.

The ethylene copolymer of the present invention can be obtained byvarious preparation methods, and no particular restriction is put onthis method, but a catalyst and polymerization conditions should besuitably selected. In this case, preferable examples of the catalystinclude alkoxytitanium compounds, and titanium and zirconium compoundsin which a crosslinking is present between ligands.

In the polymerization catalyst for use in the preparation of theethylene copolymer of the present invention, the transition metalcompounds of the component (A) may be used singly or in a combination oftwo or more thereof.

On the other hand, examples of a compound which can be used as thecomponent (B) in the polymerization catalyst and which is capable offorming an ionic complex from the transition metal compound of thecomponent (A) or its derivative include (B-1) an ionic compound forreacting with the transition metal compound of the component (A) to forman ionic complex, (B-2) an aluminoxane, and (B-3) a Lewis acid.

As the inonic compound of the component (B-1), any inonic compound canbe used, so far as it reacts with the transition metal compound of thecomponent (A) to form the ionic complex. However, there can be suitablyused a compound comprising a cation and an anion in which a plurality ofgroups are bonded to an element, particularly a coordinate complexcompound comprising a cation and an anion in which a plurality of groupsare bonded to an element. The compound comprising a cation and an anionin which a plurality of groups are bonded to an element is a compoundrepresented by the general formula

    ( L.sup.1 -R.sup.17 !.sup.k+).sub.p ( M.sup.5 Z.sup.1 Z.sup.2 . . . Z.sup.n !.sup.(h-g)-).sub.q                                       (XV)

or

    ( L.sup.2 !.sup.k+).sub.p (M.sup.6 Z.sup.1 Z.sup.2 . . . Z.sup.n !.sup.(h-g)-).sub.q                                       (XVI)

wherein L² is M⁷, R¹⁸ R¹⁹ M⁸, R²⁰ ₃ C or R²¹ M⁸. in the formulae (XV)and (XVI), L¹ is a Lewis base; M⁵ and M⁶ are each an element selectedfrom the groups 5, 6, 7, 8-10, 11, 12, 13, 14 and 15 of the periodictable, preferably an element selected from the groups 13, 14 and 15; M⁷and M⁸ are each an element selected from the groups 3, 4, 5, 6, 7, 8-10,1, 11, 2, 12 and 17 of the periodic table; Z¹ to Z^(n) are each ahydrogen atom, a dialkylamino group, an alkoxy group having 1 to 20carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an alkylgroup having 1 to 20 carbon atoms, an aryl group, an alkylaryl group oran arylalkyl group having 6 to 20 carbon atoms, a halogen-substitutedhydrocarbon having 1 to 20 carbon atoms, an acyloxy group having 1 to 20carbon atoms, an organic metalloid group or a halogen atom, and Z¹ toZ^(n) may bond to each other to form a ring. R¹⁷ is a hydrogen atom, analkyl group having 1 to 20 carbon atoms, or an aryl group, an alkylarylgroup or an arylalkyl group having 6 to 20 carbon atoms; R¹⁸ and R¹⁹ areeach a cyclopentadienyl group, a substituted cyclopentadienyl group, anindenyl group or a fluorenyl group; and R²⁰ is an alkyl group having 1to 20 carbon atoms, an aryl group, an alkylaryl group or an arylalkylgroup. R²¹ is a large cyclic ligand such as tetraphenylporphyrin orphthalocyanine. g is a valence of each of M⁵ and M⁶, and it is aninteger of 1 to 7; h is an integer of 2 to 8; k is an ion valence of L¹-R¹⁷ ! or L² ! and it is an integer of 1 to 7; and p is an integer of 1or more, and q=(p×k)/(h-g).

Here, typical examples of the Lewis base represented by the L¹ includeammonia, amines such as methylamine, aniline, dimethylamine,diethylamine, N-methylaniline, diphenylamine, trimethylamine,triethylamine, tri-n-butylamine, N,N-dimethylaniline,methyldiphenylamine, pyridine, p-bromo-N,N-dimethylaniline andp-nitro-N,N-dimethylaniline, phosphines such as triethylphosphine,triphenylphosphine and diphenylphosphine, ethers such as dimethyl ether,diethyl ether, tetrahydrofuran and dioxane, thioethers such as diethylthioether and tetrahydrothiophene, and an ester such as ethyl benzoate.

Furthermore, typical examples of M⁵ and M⁶ include B, Al, Si, P, As andSb, and B and P are preferable. Typical examples of M⁷ include Li, Na,Ag, Cu, Br and I, and typical examples of M⁸ include Mn, Fe, Co, Ni andZn. Typical examples of Z¹ to Z^(n) include a dimethylamino group and adiethylamino group as the dialkylamino group; a methoxy group, an ethoxygroup and an n-butoxy group as the alkoxy group having 1 to 20 carbonatoms; a phenoxy group, a 2,6-dimethylphenoxy group and a naphthyloxygroup as the aryloxy group having 6 to 20 carbon atoms; a methyl group,an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group,an n-octyl group and a 2-ethylhexyl group as the alkyl groups having 1to 20 carbon atoms; a phenyl group, a p-tolyl group, a benzyl group, a4-t-butylphenyl group, a 2,6-dimethylphenyl group, a 3,5-dimethylphenylgroup, a 2,4-dimethylphenyl group and a 2,3-dimethylphenyl group as thearyl groups, alkylaryl groups or arylalkyl groups having 6 to 20 carbonatoms; a p-fluorophenyl group, a 3,5-difluorophenyl group, apentachlorophenyl group, a 3,4,5-trifluorophenyl group, apentafluorophenyl group and a 3,5-di(trifluoromethyl)phenyl group as thehalogen-substituted hydrocarbons having 1 to 20 carbon atoms; F, Cl, Brand I as the halogen atoms; and a pentamethylantimony group, atrimethylsilyl group, a trimethylgermil group, a diphenylarsine group, adicyclohexylantimony group and a diphenylboron group as the organicmetalloid groups. Typical examples of R¹⁷, R²⁰ are as mentioned above.Typical examples of the substituted cyclopentadienyl group of R¹⁸ andR¹⁹ include alkyl group-substituted groups such as amethylcyclopentadienyl group, a butylcyclopentadienyl group and apentamethylcyclopentadienyl group. Here, the alkyl group usually has 1to 6 carbon atoms, and the number of the substituted alkyl groups is aninteger of 1 to 5.

Among the compounds represented by the general formulae (XV) and (XVI),the compounds in which M⁵ and M⁶ are boron are preferable. Of thecompounds of the general formulae (XV) and (XVI), typically, thefollowing examples can particularly preferably be used.

Examples of the compound of the general formula (XV) includetriethylammonium tetraphenylborate, tri(n-butyl)ammoniumtetraphenylborate, trimethylammonium tetraphenylborate,tetraethylammonium tetraphenylborate, methyltri(n-butyl)ammoniumtetraphenylborate, benzyltri(n-butyl)ammonium tetraphenylborate,dimethyldiphenylammonium tetraphenylborate, methyltriphenylammoniumtetraphenylborate, trimethylanilinium tetraphenylborate,methylpyridinium tetraphenylborate, benzylpyridinium tetraphenylborate,methyl(2-cyanopyridinium) tetraphenylborate, trimethylsulfoniumtetraphenylborate, benzylmethylsulfonium tetraphenylborate,triethylammonium tetrakis(pentafluorophenyl)borate, tri(n-butyl)ammoniumtetrakis(pentafluorophenyl)borate, triphenylammoniumtetrakis(pentafluorophenyl)borate, tetrabutylammoniumtetrakis(pentafluorophenyl)borate, tetraethylammoniumtetrakis(pentafluorophenyl)borate, methyltri(n-butyl)ammonium!tetrakis(pentafluorophenyl)borate, (benzyltri(n-butyl)ammonium!tetrakis(pentafluorophenyl)borate, methyldiphenylammoniumtetrakis(pentafluorophenyl)borate, methyltriphenylammoniumtetrakis(pentafluorophenyl)borate, dimethyldiphenylammoniumtetrakis(pentafluorophenyl)borate, aniliniumtetrakis(pentafluorophenyl)borate, methylaniliniumtetrakis(pentafluorophenyl)borate, dimethylaniliniumtetrakis(pentafluorophenyl)borate, trimethylaniliniumtetrakis(pentafluorophenyl)borate, dimethyl(m-nitroanilinium)tetrakis(pentafluorophenyl)borate, dimethyl(p-bromoanilinium)tetrakis(pentafluorophenyl)borate, pyridiniumtetrakis(pentafluorophenyl)borate, (4-cyanopyridinium)tetrakis(pentafluorophenyl)borate, (N-methylpyridinium)tetrakis(pentafluorophenyl)borate, (N-benzylpyridinium)tetrakis(pentafluorophenyl)borate, (2-cyano-N-methylpyridinium)tetrakis(pentafluorophenyl)borate, (4-cyano-N-methylpyridinium)tetrakis(pentafluorophenyl)borate, (4-cyano-N-benzylpyridinium)tetrakis(pentafluorophenyl)borate, trimethylsulfoniumtetrakis(pentafluorophenyl)borate, benzyldimethylsulfoniumtetrakis(pentafluorophenyl)borate, tetraphenylphosphoniumtetrakis(pentafluorophenyl)borate, dimethylaniliniumtetrakis(3,5-ditrifluoromethylphenyl)borate, dimethylaniliniumtris(pentafluorophenyl)(p-trifluoromethyltetrafluorophenyl)borate,triethylammoniumtris(pentafluorophenyl)(p-trifluoromethyltetrafluorophenyl)borate,pyridiniumtris(pentafluorophenyl)(p-trifluoromethyltetrafluorophenyl)borate,(N-methylpyridinium)tris(pentafluorophenyl)(p-trifluoromethyltetrafluorophenyl)borate,(2-cyano-N-methylpyridinium)tris(pentafluorophenyl)(p-trifluoromethyltetrafluorophenyl)borate,(4-cyano-N-benzylpyridinium)tris(pentafluorophenyl)(p-trifluoromethyltetrafluorophenyl)borate,triphenylphosphoniumtris(pentafluorophenyl)(p-trifluoromethyltetrafluorophenyl)borate,dimethylaniliniumtris(pentafluorophenyl)(2,3,5,6-tetrafluoropyridinyl)borate,triethylammoniumtris(pentafluorophenyl)(2,3,5,6-tetrafluoropyridinyl)borate, pyridiniumtris(pentafluorophenyl)(2,3,5,6-tetrafluoropyridinyl)borate,(N-methylpyridinium)tris(pentafluorophenyl)(2,3,5,6-tetrafluoropyridinyl)borate,(2-cyano-N-methylpyridinium)tris(pentafluorophenyl)(2,3,5,6-tetrafluoropyridinyl)borate,(4-cyano-N-benzylpyridinium)tris(pentafluorophenyl)(2,3,5,6-tetrafluoropyridinyl)borate,triphenylphosphoniumtris(pentafluorophenyl)(2,3,5,6-tetrafluoropyridinyl)borate,dimethylanilinium tris(pentafluorophenyl)(phenyl)borate;dimethylanilinium tris(pentafluorophenyl)3,5-di(trifluoromethyl)phenyl!borate, dimethylaniliniumtris(pentafluorophenyl)(4-trifluoromethylphenyl)borate,dimethylanilinium triphenyl(pentafluorophenyl)borate andtriethylammonium hexafluoroarsenate.

On the other hand, examples of the compound of the general formula (XVI)include ferrocenium tetraphenylborate, silver tetraphenylborate, trityltetraphenylborate, tetraphenylporphyrinmanganese tetraphenylborate,ferrocenium tetrakis(pentafluorophenyl)borate,(1,1'-dimethylferrocenium) tetrakis(pentafluorophenyl)borate,decamethylferrocenium tetrakis(pentafluorophenyl)borate,acetylferrocenium tetrakis(pentafluorophenyl)borate, formylferroceniumtetrakis(pentafluorophenyl)borate, cyanoferroceniumtetrakis(pentafluorophenyl)borate, silvertetrakis(pentafluorophenyl)borate, trityltetrakis(pentafluorophenyl)borate, lithiumtetrakis(pentafluorophenyl)borate, sodiumtetrakis(pentafluorophenyl)borate, tetraphenylporphyrinmanganesetetrakis(pentafluorophenyl)borate, tetraphenylporphyriniron chloridetetrakis(pentafluorophenyl)borate, tetraphenylporphyrinzinc chloridetetrakis(pentafluorophenyl)borate, silver tetrafluoroborate, silverhexafluoroarsenate and silver hexafluoroantimonate.

In addition to the compounds of the above-mentioned general formulae(XV) and (XVI), there can also be used, for example,tris(pentafluorophenyl)boron, tris 3,5-di(trifluoromethyl)phenyl!boronand triphenylboron.

The ionic compounds, which are the components (B-1), capable of reactingwith the transition metal compound of the above-mentioned component (A)to form an ionic complex may be used singly or in a combination of twoor more thereof. Furthermore, a component comprising the transitionmetal compound of the component (A) and the ionic compound, which is thecomponent (B-1), capable of forming an ionic complex may be apolycationic complex.

On the other hand, as the aluminoxane of the component (B-2), there canbe mentioned a chain aluminoxane represented by the general formula(XVII) ##STR19## (wherein R²² s are each independently a halogen atom,or a hydrocarbon group such as an alkyl group, a cycloalkyl group, analkenyl group, an aryl group or an arylalkyl group having 1 to 20 carbonatoms, preferably 1 to 12 carbon atoms, and the alkyl group is morepreferable; and s denotes a polymerization degree, and it is an integerof usually 3 to 50, preferably 7 to 40), and a cyclic aluminoxanerepresented by the general formula (XVIII) ##STR20## (wherein R²² s ands are as defined above).

Among the compounds of the general formulae (XVII) and (XVIII), thealuminoxanes having a polymerization degree of 7 or more are preferable.In the case that the aluminoxane having a polymerization degree of 7 ormore, or a mixture of these aluminoxanes is used, a high activation canbe obtained. Furthermore, modified aluminoxanes can also suitably beused which can be obtained by modifying the aluminoxanes represented bythe general formulae (XVII) and (XVIII) with a compound such as waterhaving an active hydrogen and which are insoluble in usual solvents.

As a preparation method of the above-mentioned aluminoxanes, a methodcan be mentioned in which an alkylaluminum is brought into contact witha condensation agent such as water, but no particular restriction is puton its means, and the reaction can be carried out in a known manner. Forexample, there are (1) a method which comprises dissolving an organicaluminum compound in an organic solvent, and then bringing the solutioninto contact with water, (2) a method which comprises first adding anorganic aluminum compound at the time of polymerization, and then addingwater, (3) a method which comprises reacting water of crystallizationcontained in a metallic salt or water adsorbed by an inorganic substanceor an organic substance with an organic aluminum compound, and (4) amethod which comprises reacting a tetraalkyldialuminoxane with atrialkylaluminum, and further reacting with water. These aluminoxanesmay be used singly or in a combination of two or more thereof.

Furthermore, no particular restriction is put on the Lewis acid which isthe component (B-3), and this Lewis acid may be an organic compound or asolid inorganic compound. As the organic compound, boron compounds andaluminum compounds are preferably used, and as the inorganic compound,magnesium compounds and aluminum compounds are preferably used. TheseLewis acids may be used singly or in a combination of two or morethereof.

In order to obtain the ethylene copolymer of the present invention, asthe catalytic component (B), the above-mentioned components (B-1), (B-2)and (B-3) may be used singly or in a combination of two or more thereof.

In the polymerization catalyst, if desired, as a component (C), anorganic aluminum compound can be used which is represented by thegeneral formula (XIX)

    R.sup.23.sub.r AlQ.sub.3-r                                 (XIX)

wherein R²³ is an alkyl group having 1 to 10 carbon atoms; Q is ahydrogen atom, an alkoxy group having 1 to 20 carbon atoms, an arylgroup having 6 to 20 carbon atoms or a halogen atom; and r is an integerof 1 to 3.

In particular, when the ionic compound (B-1) which is capable ofreacting with the transition metal compound of the component (A) to forman ionic complex is used as the component (B) together with the organicaluminum compound (C), a high activity can be obtained.

Typical examples of the compound represented by the general formula(XIX) include trimethylaluminum, triethylaluminum triisopropylaluminum,triisobutylaluminum, dimethylaluminum chloride, diethylaluminumchloride, methylaluminum dichloride, ethylaluminum dichloride,dimethylaluminum fluoride, diisobutylaluminum hydride, diethylaluminumhydride and ethylaluminum sesquichloride.

Next, in the present invention, at least one of the catalyst components(A), (B) and, if desired, (C) can be supported on a suitable carrier andthen used.

No particular restriction is put on the kind of carrier, and inorganicoxide carriers, other inorganic carriers and organic carriers all can beused, but the inorganic oxide carriers and the other inorganic carriersare particularly preferable.

Typical examples of the inorganic oxide carriers include SiO₂, Al₂ O₃,MgO, ZrO₂, TiO₂, Fe₂ O₃, B₂ O₃, CaO, ZnO, BaO, ThO₂ and mixturesthereof, for example, silica-alumina, zeolite, ferrite, sepiolite andglass fiber. Above all, SiO₂ and Al₂ O₃ are particularly preferable. Inthis connection, the above-mentioned inorganic oxide carrier may containa small amount of a carbonate, a nitrate, a sulfate or the like.

On the other hand, examples of the carriers other than mentioned aboveinclude magnesium compounds such as MgCl₂ and Mg(OC₂ H₅)₂ and theircomplex salts as well as organic magnesium compounds represented by thegeneral formula MgR²⁴ _(i) X³ _(j). Here, R²⁴ represents an alkyl grouphaving 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atomsor an aryl group having 6 to 20 carbon atoms; X³ is a halogen atom or analkyl group having 1 to 20 carbon atoms; i is 0 to 2; and j is 0 to 2.

Furthermore, examples of the organic carriers include polymers such aspolystyrenes, styrene-divinylbenzene copolymers, polyethylenes,polypropylenes, substituted polystyrenes and polyarylates, starch andcarbon.

The state of the carrier which can be used herein depends upon its kindand a manufacturing process, but its average particle diameter isusually in the range of 1 to 300 μm, preferably 10 to 200 μm, morepreferably 20 to 100 μm.

If the particle diameter is small, the fine power of the polymerincreases, and if the particle diameter is large, the coarse particlesof the polymer increase, which causes the deterioration of a bulkdensity and the clogging of a hopper.

Moreover, the specific surface area of the carrier is usually in therange of 1 to 1000 m² /g, preferably 50 to 500 m² /g, and its porevolume is usually in the range of 0.1 to 5 cm³ /g, preferably 0.3 to 3cm³ /g.

If either of the specific surface area and the pore volume deviates fromthe above-mentioned range, a catalyst activity deteriorates sometimes.In this connection, the specific surface area and the pore volume can becalculated from the volume of an adsorbed nitrogen gas in accordancewith a BET method refer to Journal of the American Chemical Society,Vol. 60, p. 309 (1983)!.

Furthermore, it is desirable that the above-mentioned carrier, whenused, is calcined usually at 150° to 1000° C., preferably 200° to 800°C.

No particular restriction is put on a method for supporting thecatalytic components on the carrier, and a conventional usual method canbe used.

Next, a ratio between the respective catalytic components which can beused in the present invention will be described. In the case (1) thatthe catalytic components (A) and (B-1) are used, both the components aresuitably used so that a molar ratio of the component (A)/the component(B-1) may be in the range of 1/0.1 to 1/100, preferably 1/0.5 to 1/10,more preferably 1/1 to 1/5. In the case (2) that the catalyticcomponents (A), (B-1) and (C) are used, a molar ratio of the component(A)/the component (B-1) is the same as in the above-mentioned case (1),but a molar ratio of the component (A)/the component (C) is in the rangeof 1/2,000 to 1/1, preferably 1/1,000 to 1/5, more preferably 1/500 to1/10.

Furthermore, in the case (3) that the catalytic components (A) and (B-2)are used, both the components are suitably used so that a molar ratio ofthe component (A)/the component (B-2) may be in the range of 1/20 to1/10,000, preferably 1/100 to 1/5,000, more preferably 1/200 to 1/2,000.In the case (4) that the catalytic components (A), (B-2) and (C) areused, a molar ratio of the component (A)/the component (B-2) is the sameas in the above-mentioned case (3), but a molar ratio of the component(A)/the component (C) is in the range of 1/2,000 to 1/1, preferably1/1,000 to 1/5, more preferably 1/500 to 1/10.

In addition, in the case (5) that the catalytic components (A) and (B-3)are used, both the components are suitably used so that a molar ratio ofthe component (A)/the component (B-3) may be in the range of 1/0.1 to1/2,000, preferably 1/0.2 to 1/1,000, more preferably 1/0.5 to 1/500. Inthe case (6) that the catalytic components (A), (B-3) and (C) are used,a molar ratio of the component (A)/the component (B-3) is the same as inthe above-mentioned case (5), but a molar ratio of the component (A)/thecomponent (C) is in the range of 1/2,000 to 1/1, preferably 1/1,000 to1/5, more preferably 1/500 to 1/10.

In the present invention, an ethylene copolymer, in which the activationenergy (Ea) of melt flow and a Huggins coefficient are controlled andnon-Newtonian properties are improved and which is excellent in workingproperties, can efficiently be obtained by polymerizing ethylene and anolefin having 3 to 20 carbon atoms in the presence of a catalystcomprising (a) a transition metal compound in which the relation betweena monomer charge composition a molar ratio M! of1-octene/(ethylene+1-octene)! and the product of a crystallizationenthalpy (ΔH) and a melting point (Tm) of a produced copolymer meets theequation

    0≦ΔH·Tm≦27,000-21,600  M!.sup.0.56

(however, under polymerization conditions using the component (a)together with an aluminoxane), (b) a transition metal compound capableof forming a terminal vinyl group in the homopolymerization of ethyleneor the copolymerization of ethylene and at least one ethylene selectedfrom olefins having 3 to 20 carbon atoms (however, under polymerizationconditions using the component (b) together with the aluminoxane), and(c) a compound capable of forming an ionic complex from theabove-mentioned components (a) and (b) or their derivatives, whichcomponents (a) and (b) are selected from transition metal compounds ofthe components (A) which contain a metal in the groups 3 to 10 of theperiodic table or in a lanthanide series, preferably titanium,zirconium, hafnium, chromium, vanadium or a metal in the lanthanideseries, and which component (c) is selected from B!.

Also in the case that such a polymerization catalyst is used, asdescribed above, the organic aluminum compound which is theabove-mentioned component (C) may additionally be used, and at least oneof the catalytic components may be supported on the suitable carrier.Furthermore, a use ratio between the component (a) and the component (b)depends upon a single catalytic activity of each component, and so itcannot sweepingly be decided, but when the ratio of the component (a) isincreased, the ethylene copolymer having the high non-Newtonianproperties can be obtained. In general, the molar ratio of the component(a)/the component (b) is selected in a range of 1/1,000 to 1,000/1,preferably 1/500 to 500/1, more preferably 1/300 to 300/1.

The transition metal compound which is the component (a) has thecatalytic component whose copolymerization properties are in a specificrange, and on the other hand, the transition metal compound which is thecomponent (b) is the catalytic component capable of forming a terminalvinyl group. When such two kinds of transition metal compounds arecombined and used, the ethylene copolymer having the non-Newtonianproperties can be obtained. The fact that the ethylene copolymer has thenon-Newtonian properties is supposed to be due to the presence oflong-chain branches, and in view of the formation mechanism of thebranches, it can be presumed that a comb-shaped polymer is not merelyproduced but a branch is further formed on the branched chain in thesystem.

Next, reference will be made to the formation of the terminal vinylgroup and copolymerization properties by the above-mentioned catalyst.

(1) Formation of terminal vinyl group

The formation of the terminal vinyl group is usually considered to bedue to the elimination chain transfer of β hydrogen and a β alkyl groupat the growing terminal in a polymerization system in which ethylene orpropylene is concerned. It can be determined by evaluating a polymerproduced by ethylene polymerization or copolymerization using thetransition metal compound of the component (b) and the aluminoxanewhether or not the catalyst has the ability of forming the terminalvinyl group. However, in the case that the production of the polymer issmall, it is necessary to employ polymerization conditions for molecularweight reduction such as the increase in a catalyst concentration andthe decrease in a monomer concentration.

The determination of the terminal vinyl group can be carried out bycalculating the number n of the terminal vinyl groups with respect to100 carbon atoms on the basis of a peak of the terminal vinyl groupwhich appears at 907 cm⁻¹ by IR measurement in accordance with theequation

    n=0.114×A.sub.907 /(d×T)

wherein A₉₀₇ is an absorbance at 907 cm⁻¹ ; d is density (g/ml); and Tis a thickness of a film to be measured.

As the catalytic component which can produce the polymer having a largenumber of the terminal vinyl groups thus calculated, i.e., the suitablyusable transition metal compound of the component (b), there can bementioned compounds containing a metal such as titanium, zirconium,hafnium, vanadium or chromium.

The number of the terminal vinyl groups does not always mean theeasiness of the production of the vinyl groups, because when thecatalyst is used which can easily produce the vinyl groups and caneasily react the vinyl groups with the monomer to form the branches, thenumber of the vinyl groups finally becomes small. On the contrary, whenthe catalyst is used which can easily form the vinyl groups and has thebad copolymerization properties, many vinyl groups remain.

Thus, it is necessary to inspect the easiness of the branch formation.This can be evaluated by a ratio between a number-average molecularweight Mn in terms of the polyethylene measured by gel permeationchromatography (GPC) and a number-average molecular weight Mn calculatedon the basis of a ratio between the methylene groups on the main chainand the terminal groups measured by ¹ H-NMR. In carrying out the branchevaluation on the basis of this Mn ratio, it is necessary tocomprehensively judge and determine the Mn ratio in consideration of (1)that the Mn measured by the GPC does not always denote a real molecularweight in the case that the polymer has a branch structure, and (2) thatwhen a molecular weight distribution is wide, the accuracy of the Mnvalue is low.

Preferable examples of the transition metal compound as the catalyticcomponent (b) having such terminal vinyl group formation propertiesinclude

(1) compounds having a --OR group (wherein R is an alkyl group, an arylgroup, an alkylaryl group, an arylalkyl group, a cycloalkyl group, ahalogenated alkyl group or a halogenated aryl group having 1 to 20carbon atoms),

(2) compounds represented by the formula (II)

    Cp.sub.2 M.sup.1 R.sup.1.sub.a R.sup.2.sub.b               (II)

(3) compounds represented by the formula (III)

    (Cp-A.sub.e -Cp)M.sup.1 R.sup.1.sub.a R.sup.2.sub.b        (III)

(wherein Cp, A, M¹, R¹, R², a, b and e are as defined above)

(2) Copolymerization properties

In order to copolymerize the formed terminal vinyl group with ethyleneor another comonomer, high copolymerization properties are required. Inparticular, the copolymerization properties of a high α-olefin usuallyextremely deteriorate, as the number of carbon atoms decreases and theratio of the vinyl group per molecular weight decreases.

In the present invention, a copoymerization system is required in whichthe relation between a monomer composition ratio a molar ratio M! of1-octene/(ethylene+1-octene)! and the product of a crystallizationenthalpy (ΔH) and a melting point (Tm) of a produced copolymer meets theequation

    0≦ΔH·Tm≦27,000-21,600  M!.sup.0.56

and in order to meet the requirements, the transition metal compoundwhich is the component (a) is used. Furthermore, the polymerizationconditions are evaluated by selecting excellent polymerizable conditionsusing the transition metal compound of the component (a) and thealuminoxane.

(Method for verifying the relation of the above equation)

The crystallization enthalpy (ΔH) can be obtained as follows. That is tosay, the crystallization enthalpy (ΔH) (unit=J/g) can be calculated onthe basis of an exothermic peak of crystallization observed at a timewhen a sample sheet hot-pressed at a temperature of 190° C. is molten ata temperature of 150° C. for 5 minutes by the use of a differentialscanning calorimeter (DSC7 model, made by Perkin Elmer Co., Ltd.), andthen cooled to -50° C. at a rate of 10° C./min.

On the other hand, copolymerization conditions are (1) that thepolymerization may be carried out under atmospheric pressure or anincreased pressure, (2) that batch polymerization in which ethylenealone is continuously fed (however, a monomer conversion=20% or less),or continuous polymerization is acceptable, (3) that a polymerizationtemperature is within ±10° C. of a temperature at which a maximumpolymerization activity is obtained, or a temperature at which thepolyethylenic polymer having the non-Newtonian properties can beprepared in an actual mixed catalyst system, (4) that copolymerizationreaction is initiated after a composition ratio between ethylene and thecomonomer and the total concentration have reached a steady state, (5)that the molecular weight of the produced copolymer is more than acritical molecular weight, and the polymerization must not be carriedout in a region where a melting point increases with the increase in themolecular weight, (6) that an ethylene concentration and a gaseousmonomer concentration are calculated on the basis of the weight of theethylene or the monomer which is dissolved in a polymerization solventand with which the polymerization solvent is saturated at a certaintemperature, (7) that in the case of gaseous polymerization, a monomercharge composition ratio is calculated on the basis of a partialpressure or a monomer feed ratio, (8) that polymerization conditionsunder which a monomer composition in the system changes by the diffusionof ethylene or a gaseous monomer are unacceptable, (9) that thepolymerization must not be continued in a condition that ethylene is notconsumed by the polymerization, and (10) that the molar ratio betweenthe respective catalytic components is such that the transition metalcompound (a)/aluminoxane is in the range of 1/100 to 1/2,000.

The relation between a monomer charge composition ratio M! and theproduct of the ΔH and the melting point (Tm) of the produced ethylenicpolymer is required to meet the equation

    0≦ΔH·Tm≦27,000-21,600  M!.sup.0.56

and if the product of the ΔH and the melting point (Tm) is more thanthis range, the transition metal compound (a) does not exert thepreferable copolymerization properties.

This relation is preferably

    0≦ΔH·Tm≦27,000-22,000  M!.sup.0.53

more preferably

    0≦ΔH·Tm≦27,000-23,000  M!.sup.0.53

further preferably

    0≦ΔH·Tm≦27,000-24,000  M!.sup.0.47

further more preferably

    0≦ΔH·Tm≦27,000-26,000  M!.sup.0.40

most preferably

    0≦ΔH·Tm≦27,000-27,000  M!.sup.0.27.

Preferable examples of the transition metal compound which is thecatalytic component (a) having such copolymerization properties includecompounds represented by the general formulae

    CpM.sup.1 R.sup.1.sub.a R.sup.2.sub.b R.sup.3.sub.c        (I)

    (Cp-A.sub.e -Cp)M.sup.1 R.sup.1.sub.a R.sup.2.sub.b        (III) ##STR21## and ##STR22## wherein Cp, A, E, E.sup.1, E.sup.2, E.sup.3, E.sup.4, M.sup.1, M.sup.3, X.sup.2, Y.sup.2, Y.sup.4, Z, R.sup.1 to R.sup.3, a, b, c, e, w, m, v, v', x and x' are as defined above. Of these compounds, titanium compounds, zirconium compounds and vanadium compounds are more preferable. Above all, the compounds represented by the formulae (VI) and (III) are particularly preferable, because of having a high polymerization activity.

The polymerization using the above-mentioned catalyst can be carried outby one-step polymerization or the following two-step polymerization inthe presence of the catalytic components (a), (b) and (c). That is tosay, ethylene is homopolymerized in the presence of the catalytic systemcomprising the components (b) and (c) to substantially produce apolymer, and the catalytic component (a) is then added to thepolymerization system to continue the polymerization. According to thisprocess, the control of a molecular weight distribution is possible, anda branching degree distribution can be changed. Therefore, a moleculardesign which can comply with the requirement of physical properties in awide range is possible. Furthermore, in the two-step polymerization, theethylene copolymer can be provided in which the amount of carbon-carbonunsaturated bonds in the produced copolymer decreases and thermalstability is improved. On the other hand, the ethylene copolymerobtained by the one-step polymerization is suitable for a material for achemically modifiable ethylenic polymer, because of having relativelylarge unsaturated groups. In this two-step polymerization, the comonomermay be fed to the polymerization step which is the second step, or maybe fed to both of the polymerization steps which are the first andsecond steps.

In the present invention, no particular restriction is put on apolymerization method for preparing the ethylene copolymer, and therecan be utilized a solvent polymerization method using an inerthydrocarbon or the like (a suspension polymerization or a solutionpolymerization), a bulk polymerization method in which thepolymerization is carried out in the substantial absence of an inerthydrocarbon solvent, and a gaseous phase polymerization method.

Examples of a hydrocarbon solvent which can be used in thepolymerization include saturated hydrocarbons such as butane, heptane,hexane, heptane, octane, nonane, decane, cyclopentane and cyclohexane;aromatic hydrocarbons such as benzene, toluene and xylene; andchlorine-containing solvents such as chloroform, dichloromethane,ethylene dichloride and chlorobenzene.

Polymerization temperature is usually in the range of -100° to 200° C.,preferably -50° to 100° C., more preferably 0° to 100° C., andpolymerization pressure is usually in the range of atmospheric pressureto 100 kg/cm², preferably atmospheric pressure to 50 kg/cm², morepreferably atmospheric pressure to 20 kg/cm².

The control of the molecular weight of the obtained polymer is carriedout by a usual means, for example, (1) hydrogen, (2) temperature, (3) amonomer concentration or (4) a catalyst concentration.

In a hydrogenation treatment of the ethylene copolymer above obtained, ahydrogenation catalyst can be used. No particular restriction is put onthe kind of hydrogenation catalyst, and there can be employed thecatalysts previously mentioned in detail and catalysts which can usuallybe used at the time of the hydrogenation of an olefin compound. Forexample, the following catalysts can be mentioned.

Examples of a heterogeneous catalyst include nickel, palladium andplatinum as well as solid catalysts obtained by supporting these metalson carriers such as carbon, silica, diatomaceous earth, alumina andtitanium oxide, for example, nickel-silica, nickel-diatomaceous earth,palladium-carbon, palladium-silica, palladium-diatomaceous earth andpalladium-alumina. Examples of the nickel catalyst include Raney nickelcatalysts, and examples of the platinum catalyst include a platinumoxide catalyst and platinum black. Examples of a homogeneous catalystinclude catalysts containing metals in the groups 8 to 10 of theperiodic table as basic components, for example, catalysts comprising Niand Co compounds and organic metallic compounds of metals selected fromthe groups 1, 2 and 3 of the periodic table such as cobaltnaphthenate-triethylaluminum, cobalt octenoate-n-butyllithium, nickelacetylacetonato-triethylaluminum, and Rh compounds.

In addition, Ziegler hydrogenation catalysts disclosed by M. S. Saloanet al. J. Am. Chem. Soc., 85, p. 4014 (1983)! can also effectively used.Examples of these catalysts include the following compounds.

Ti(O-iC₃ H₇)₄ -(iC₄ H₉)₃ Al,

Ti(O-iC₃ H₇)₄ -(C₂ H₅)₃ Al,

(C₂ H₅)₂ TiCl₂ -(C₂ H₅)₃ Al,

Cr(acac)₃ -(C₂ H₅)₃ Al

(wherein acac represents acetylacetonato),

Na(acac)-(iC₄ H₉)₃ Al,

Mn(acac)₃ -(C₂ H₅)₃ Al,

Fe(acac)₃ -(C₂ H₅)₃ Al,

Ca(acac)₂ -(C₂ H₅)₃ Al, and

(C₇ H₅ COO)₃ Co-(C₂ H₅)₃ Al.

The amount of the catalyst to be used in the hydrogenation step issuitably selected so that a molar ratio of the remaining unsaturatedgroups to the hydrogenation catalyst components in the ethylenecopolymer may be in the range of 10⁷ :1 to 10:1, preferably 10⁶ :1 to10² :1.

Furthermore, the charge pressure of hydrogen is suitably in the range offrom atmospheric pressure to 50 kg/cm² G. Besides, a reactiontemperature is preferably on a higher side in the range in which theethylene copolymer obtained in the polymerization process do notdecompose, and it is usually selected in the range of -100° to 300° C.,preferably -50° to 200° C., more preferably 10° to 180° C.

Next, the present invention will be described in more detail withreference to examples, but the scope of the present invention should notbe limited to these examples.

EXAMPLE 1

(1) Preparation of catalytic component

A 100-ml egg-plant type flask was dried and purged with nitrogen, and 30ml of toluene and 3.6 ml of an n-butylithium solution in hexane (1.66mols/l) were then placed in the flask, followed by cooling the solutionto -78° C. Afterward, 0.56 g of cyclopentanol was added dropwisethereto, and the solution was then warmed up to -50° C. over 60 minutes.Next, 26 ml of a pentamethylcyclopentadiene trichloride titaniumsolution in toluene (0.0769 mol/l) was added dropwise to the solutionover 60 minutes. The solution was further warmed up to -25° C., andreaction was then carried out for 120 minutes. Afterward, the solutionwas warmed up to 20° C., and then allowed to stand for 24 hours. Theresultant reaction solution was light yellow, and a white precipitate oflithium chloride was produced on the bottom of the flask.

(2) Preparation of methylaluminoxane

In a 500-ml glass container which had been purged with argon were placed200 ml of toluene, 17.8 g (71 mmols) of copper sulfate pentahydrate(CuSO₄ ·5H₂ O) and 24 ml (250 mmols) of trimethylaluminum, and themixture was then reacted at 40° C. for 8 hours. Afterward, from asolution obtained by removing solid components, toluene was furtherdistilled off under reduced pressure to obtain 6.7 g of a catalyticproduct (methylaluminoxane). Furthermore, this product was subjected toa heat treatment at 120° C. for 10 hours under reduced pressure, andthen dissolved and dispersed in toluene.

(3) Preparation of ethylene/1-butene copolymer

Under a nitrogen atmosphere, 300 ml of toluene and 30 mmol ofmethylaluminoxane prepared in the above-mentioned (2) were placed in a1-liter flask equipped with a stirrer. Afterward, the solution washeated up to 60° C., and an ethylene gas was then introduced thereintounder atmospheric flow conditions to saturate the flask with theethylene gas. Furthermore, 1-butene was continuously fed. Next, 9 ml ofthe solution portion alone of the catalytic component prepared in theabove-mentioned (1) was thrown into the flask.

Reaction temperature was controlled to 60° C., and polymerization wascarried for 120 minutes while ethylene and 1-butene were continuouslyfed. At this time, the total amount of the fed 1-butene was 5.5 g. Afterthe completion of the polymerization, a large amount of methanol wasthrown thereinto, followed by washing and then drying under reducedpressure, to obtain 15.4 g of ethylene-1-butene copolymer.

(4) Evaluation of ethylene-1-butene copolymer

(a) Measurement of Huggins coefficient

In 15.691 g of decalin was dispersed 0.0444 g of the copolymer obtainedin the above-mentioned (3) at 135° C. The concentration of the polymerobtained was 0.2237 g/dl in the case that the density of the decalin at135° C. was 0.79055 g/ml. The reduced viscosity of the polymer at 135°C. measured by a Ubbelode's viscometer was 2.778 dl/g. Furthermore, thisviscosity measurement was carried out at 6 points at a substantiallyequal interval in the same manner as described above, while the polymeras a mother liquor was diluted with decalin.

A Huggins coefficient determined by the above-mentioned measurement was0.494, an intrinsic viscosity η! was 2.22 dl/g, and a correlationcoefficient was 0.998. Moreover, the Huggins coefficient of astraight-chain ethylene polymer having η!=2.22 dl/g prepared by the useof a titanium tetrachloride/triethylaluminum catalyst was 0.365, and theratio between these Huggins coefficients was 1.35.

Furthermore, the Huggins coefficient of ethylene/1-butene copolymerhaving η!=2.22 dl/g prepared by the use of a titaniumtetrachloride/triethylaluminum catalyst was 0.410, and the ratio betweenboth the Huggins coefficients was 1.21.

(b) Structure analysis by NMR

The measurement of ¹³ C-NMR measurement temperature=130° C.,solvent=1,2,4-trichlorobenzene/heavy benzene (molar ratio=8/2), 100 MHz!was carried out. The results are shown in FIG. 2.

Any absorption of a methyl group in the vicinity of a quaternary carbonatom which would be observed at 8.15 ppm in an LDPE was not observed,and an ethyl branch was observed at 11.14 ppm. Judging from a fact thatthe absorptions of methine carbon and methylene carbon are present at38-39 ppm and 34-36 ppm, respectively, it can be considered that a longchain branch is also present.

(c) Evaluation of thermal behavior

A sheet hot-pressed at a temperature of 190° C. was used as a sample,and measurement was made by the use of a differential scanningcalorimeter DSC7 model made by Perkin Elmer Co., Ltd. That is to say, acrystallization enthalpy (ΔH) was calculated on the basis of anexothermic peak of crystallization observed at a time when the sheet wasmolten at a temperature of 150° C. for 5 minutes, and then cooled to-50° C. at a rate of 10° C./min. A melting point (Tm) was obtained froman endothermic peak observed at a time when the sheet was heated at arate of 10° C./min.

As a result, neither the crystallization enthalpy (ΔH) nor the meltingpoint (Tm) was observed, and hence the sheet was amorphous.

(d) Measurement of density

A sample molded by hot press at 190° C. was used, and measurement wasmade in accordance with a density gradient tube method. As a result, thedensity was 0.886 g/cm³. In addition, the annealing treatment of thesample was not carried out.

(e) Measurement of terminal vinyl groups

A hot pressed sheet having a thickness of 100 μm was prepared, and atransmitted infrared absorption spectrum was measured. The number ofterminal vinyl groups was calculated on the basis of an absorbance(A₉₀₇) based on the terminal vinyl groups in the vicinity of 907 cm⁻¹, afilm thickness (t) and a resin density (d) in accordance with theequation

    n=0.114A.sub.907 / d·t!

wherein d=g/cm³, t=mm, and n=the number of the vinyl groups with respectto 100 carbon atoms. As a result, the number of the terminal vinylgroups was 0.67 with respect to 1,000 carbon atoms.

(f) Measurement of molecular weight distribution

A molecular weight in terms of the polyethylene was measured by the useof a device: Waters ALC/GPC150C, a column: TSK HM+GMH6×2 made by TosoCo., Ltd., a solvent: 1,2,4-trichlorobenzene, a temperature: 135° C. anda flow rate: 1 ml/min in accordance with a GPC method. As a result, aratio Mw/Mn of a weight-average molecular weight to a number-averagemolecular weight was 3.05, and the weight-average molecular weight (Mw)was 153,000.

(g) Measurement of activation energy (Ea) of melt flow

The activation energy (Ea) of melt flow was measured by the use of adevice RMS E-605 made by Rheometrics Co., Ltd. in accordance with thefollowing procedure. That is to say, frequency dependences (10⁻² to 10²rad/sec) of dynamic viscoelastic properties were measured at measurementtemperatures of 150° C., 170° C., 190° C., 210° C. and 230° C., and theactivation energy (Ea) was then calculated on the basis of the shiftfactors of G', G" at the respective temperatures and the reciprocalnumber of an absolute temperature in accordance with the Arrhenius'equation by the use of a temperature-time conversion rule in which 170°C. was used as a standard temperature.

As a result, the activation energy (Ea) was 12.0 kcal/mol. In thisconnection, the Ea of an HDPE was 6.3 kcal/mol Polym. Eng. Sci., Vol. 8,p. 235 (1968)!.

EXAMPLE 2 (Ethylene-1-Butene Copolymer)

Under a nitrogen atmosphere, 400 ml of toluene, 0.25 mmol (2 mol/l) of atriisobutylaluminum solution in toluene and 30 mmol of methylaluminoxaneprepared in Example 1-(2) were placed in a 1-liter pressure-resistantautoclave equipped with a stirrer, and the solution was then heated upto 70° C. Afterward, 3.26 g of 1-butene was poured into the solution,followed by stirring for 5 minutes. Afterward, the autoclave wassaturated with ethylene under a pressure of 9.0 kg/cm² G, and 9 ml of acatalyst prepared in Example 1-(1) was thrown thereinto via a balanceline to initiate polymerization.

While the ethylene pressure was controlled so that the total pressuremight be 9.6 kg/cm² G, the polymerization was carried out for 60minutes. After the completion of the polymerization, the resultantpolymer was collected. The results are shown in Table 2.

EXAMPLE 3 (Ethylene-1-Octene Copolymer)

The same procedure as in Example 2 was carried out except that 2 ml of1-octene was used in place of 1-butene and there were employed 10 mmolof methylaluminoxane prepared in Example 1-(2), 1.5 ml of a catalyticcomponent prepared in Example 1-(1), an ethylene pressure of 7.5 kg/cm²G and a polymerization temperature of 70° C. The results are shown inTable 2.

EXAMPLE 4 (Ethylene-1-Butene Copolymer)

The same procedure as in Example 1 was carried out except that inExample 1-(2), 0.25 ml (2 mol/l) of a triisobutylaluminum solution intoluene was thrown into a toluene solvent and the solution was thenadded to a polymerization system, and 0.4 mmol of aniliniumtetrakis(pentafluorophenyl)borate was added in place ofmethylaluminoxane, thereby preparing ethylene-1-butene copolymer. Theresults are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                  Example                                                                       1      2         3        4                                         ______________________________________                                        Yield (g)   15.4     31.1      8.6    16.3                                    Intrisic Viscosity  η!                                                                2.22      3.51     0.89   2.79                                    (dl/g)                                                                        k.sup.1      0.494     0.594    0.394  0.458                                  k.sup.2      0.365     0.472    0.275  0.395                                  k.sup.3       0.410!    0.478!   0.325!                                                                               0.410!                                k.sup.1 /k.sup.2                                                                          1.35      1.26     1.43   1.16                                    k.sup.1 /k.sup.3                                                                          1.21      1.24     1.21   1.12                                    Tm (°C.)                                                                           --       89.1      123.1  114.2                                   ΔH (J/g)                                                                            --         125      195     115                                   Density (g/cm.sup.3)                                                                       0.886     0.909    0.957  0.904                                  .sup.13 C-NMR                                                                             *1       *1        *2     *1                                      Mw          153000   258000    48100  273000                                  Mw/Mn       3.05     92.2      16.1   30.5                                    Terminal Vinyl Group                                                                      0.67      2.4      3.5    0.16                                    (groups/1000 carbon                                                           atoms)                                                                        Activation Energy of                                                                      12.0     12.1      11.5   9.7                                     Melt Flow                                                                     ______________________________________                                         Activation energy of melt flow: (kcal/mol)                                    (Notes)                                                                       k.sup.1 : The Huggins coefficient of a copolymer in each example.             k.sup.2 : The Huggins coefficient of a straightchain ethylene polymer         having the same  η!.                                                      k.sup.3 : The Huggins coefficient of a straightchain ethyleneolefin           copolymer (whose density was substantially the same as in each example)       having the same  η!.                                                      Tm: Melting point                                                             ΔH: Crystallization enthalpy                                            Mw: Weightaverage molecular weight                                            Mn: Numberaverage molecular weight                                            *1: No absorption was present at 8.15 ppm, and an ethyl branch was presen     at 11.14 ppm.                                                                 *2: No absorption was present at 8.15 ppm, and an ethyl branch was presen     at 14.02 ppm.                                                            

EXAMPLE 5

The ethylene/1-octene copolymer obtained in Example 3 was hydrogenatedunder conditions of a temperature of 140° C., a polymer concentration of2% by weight, a hydrogen pressure of 30 kg/cm² G, a carbon-supportingruthenium catalyst (a Ru content=5% by weight) concentration of 4% byweight and a reaction time of 6 hours in a decalin solvent, and theobtained polymer was then isolated from the reaction solution.

From this polymer, a hot pressed sheet having a thickness of 300 μm wasformed, and an infrared absorption spectrum was then measured. As aresult, any absorption of unsaturated groups present in the range of 885to 907 cm⁻¹ was not observed.

EXAMPLE 6

(1) Preparation of catalytic component

The same procedure as in Example 1-(1) was carried out except that 0.56g of cyclopentanol was replaced with 0.38 g of isopropanol, to prepare acatalytic component.

(2) Preparation of methylaluminoxane

Methylaluminoxane was prepared in the same manner as in Example 1-(2).

(3) Preparation of ethylene/1-octene copolymer

Under a nitrogen flow, 200 ml of toluene, 2 ml of 1-octene and 20 mmolof methylaluminoxane (MAO) prepared in the above-mentioned (2) wereplaced in a stainless steel autoclave, and the mixture was then heatedup to 60° C. Afterward, nitrogen was replaced with ethylene, andethylene was fed for 10 minutes, while the solution was stirred.Afterward, 0.1 mmol of, in terms of titanium, the titanium catalyticcomponent prepared in the above-mentioned (1) and 0.67 micromol ofethylenebisindenylzirconium dichloride were promptly added, therebyinitiating the copolymerization of ethylene and 1-octene.

While ethylene was fed, reaction was carried out for 120 minutes, andthe reaction solution was then poured into methanol to sufficientlyremove ash and wash the solution, and then dried under reduced pressureto obtain 16.5 g of ethylene/1-octene copolymer.

(4) Evaluation of ethylene/1-octene copolymer

(a) Measurement by NMR

The measurement of ¹ H-NMR 400 MHz, measurement temperature=130° C.,solvent=1,2,4-trichlorobenzene/heavy benzene (molar ratio=8/2)! wascarried out. As a result, a molar ratio of CH₃ /CH₂ ! calculated on thebasis of an integrated value of the absorption of a methyl group at0.8-1.0 ppm and the absorption of a methylene group at 1.2-1.4 ppm was0.015. Furthermore, ¹³ C-NMR was measured in the same manner, and as aresult, any absorption was not observed at 8.15 ppm of a methyl group inthe vicinity of a quaternary carbon atom which would be observed in anLDPE. In addition, any absorption at 14.02, 22.28 and 27.28 ppm whichwere considered to correspond to a hexyl branch derived from 1-octenewas not observed.

(b) Evaluation of thermal behavior

A sheet hot-pressed at a temperature of 190° C. was used as a sample,and measurement was made by the use of a differential scanningcalorimeter DSC7 model made by Perkin Elmer Co., Ltd. That is to say, amelting point (Tm) was obtained from an endothermic peak observed at atime when the sheet was molten at a temperature of 150° C. for 5minutes, cooled to -50° C. at a rate of 10° C./min, and then heated at arate of 10° C./min.

As a result, the melting point (Tm) was 99.6° C.

(c) Measurement of density

Measurement was made in the same manner as in Example 1-(4)-(d). As aresult, the density was 0.9023 g/cm³. In addition, the annealingtreatment of the sample was not carried out.

(d) Measurement of molecular weight distribution

Measurement was carried out in the same manner as in Example 1-(4)-(f),and as a result, a weight-average molecular weight (Mw) was 139,000, anumber-average molecular weight (Mn) was 63,000, and an Mw/Mn ratio was2.2.

(e) Measurement of activation energy (Ea) of melt flow

Measurement was carried out in the same manner as in Example 1-(4)-(g),and as a result, an activation energy (Ea) was 11.8 kcal/mol.

EXAMPLES 7 TO 9

Each ethylene copolymer was prepared in accordance with conditions shownin Table 3. The results are shown in Table 4.

                  TABLE 3 (I)                                                     ______________________________________                                                              Transition Metal                                        Toluene   1-octene 1-hexane MAO   Components                                  (ml)      (mmol)   (mmol)   (mmol)                                                                              Kind   (mmol)                               ______________________________________                                        Exam- 200     2        --     20    Titanium                                                                             0.1                                ple 6                               compo-                                                                        nent                                                                          Zirconium                                                                            0.0067                                                                 compo-                                                                        nent                                      Exam- 200     --       1      20    Titanium                                                                             0.1                                ple 7                               compo-                                                                        nent                                                                          Zirconium                                                                            0.0067                                                                 compo-                                                                        nent                                      Exam- 200     1        --     20    Titanium                                                                             0.1                                ple 8                               compo-                                                                        nent                                                                          Zirconium                                                                            0.01                                                                   compo-                                                                        nent                                                                          Zirconium                                                                            0.001                                                                  compo-                                                                        nent                                      Exam- 400     1        --     20    Titanium                                                                             0.1                                ple 9                               compo-                                                                        nent                                                                          Zirconium                                                                            0.02                                                                   compo-                                                                        nent                                      ______________________________________                                         (Notes)                                                                       Titanium component: Catalyst prepared in Example 6(1), and "mmol" was a       value in terms of titanium.                                                   Zirconium component: Ethylenebisindenylzirconium dichloride              

                  TABLE 3 (II)                                                    ______________________________________                                        Ethylene Pressure                                                                             Temperature                                                   (kg/cm.sup.2 G) (°C.)                                                                            Time (min)                                                                              Yield (g)                                 ______________________________________                                        Example 6                                                                             Flowable    60        120     16.5                                    Example 7                                                                             Flowable    60        100     17.0                                    Example 8                                                                             Flowable    90        120     7.0                                     Example 9                                                                             Flowable    60        120     43.2                                    ______________________________________                                    

                  TABLE 4 (I)                                                     ______________________________________                                                                Weight-                                                                       Average  Molecular                                                            Molecular                                                                              Weight                                              Density                                                                             Branching  Weight   Distribution                                        (g/cm.sup.3)                                                                        Degree      Mw!      Mw/Mn!                                      ______________________________________                                        Example 6                                                                              0.902   0.026      141,000                                                                              2.8                                        Example 7                                                                              0.907   0.023      145,000                                                                              2.3                                        Example 8                                                                              0.916   0.020       93,000                                                                              2.7                                        Example 9                                                                              0.935   0.012      234,000                                                                              2.5                                        ______________________________________                                         (Note)                                                                        The branching degree: A  CH.sub.3 /CH.sub.2 ! molar ratio calculated by       .sup.1 HNMR.                                                             

                  TABLE 4 (II)                                                    ______________________________________                                        Activation Energy   Melting                                                   of Melt Flow  Ea!   Point                                                     (kcal/mol)          (°C.)                                                                          .sup.13 C-NMR                                     ______________________________________                                        Example 6                                                                            11.8              99.6   A                                             Example 7                                                                            12.1              95.0   B                                             Example 8                                                                            12.0             110.3   A                                             Example 9                                                                            11.8             117.5   A                                             ______________________________________                                         (Notes)                                                                       A: No absorption was present at 8.15 ppm, and the absorption was present      at 14.02, 22.28 and 27.88 ppm.                                                B: No absorption was present at 8.15 ppm, and the absorption was present      at 14.08 and 23.36 ppm.                                                  

EXAMPLE 10

The ethylene/1-octene copolymer obtained in Example 6 was hydrogenatedunder conditions of a temperature of 140° C., a copolymer concentrationof 9% by weight, a hydrogen pressure of 30 kg/cm² G, a carbon-supportingruthenium catalyst (a Ru content=5% by weight) concentration of 4% byweight and a reaction time of 6 hours in a decalin solvent, and theobtained polymer was then isolated from the reaction solution.

From this polymer, a hot pressed sheet having a thickness of 300 μm wasformed, and an infrared absorption spectrum was then measured. As aresult, any absorption of unsaturated groups present in the range of 885to 907 cm⁻¹ was not observed.

In addition, density, molecular weight, a melting point and fluidactivation energy were the same as in Example 6.

COMPARATIVE EXAMPLE 1

Ethylene/1-octene copolymer was prepared under conditions shown in Table5, and polymerization conditions and evaluation results are shown inTables 5 and 6.

                  TABLE 5                                                         ______________________________________                                                       Comp. Example 1                                                ______________________________________                                        Toluene (ml)     400                                                          MAO (mmol)       3                                                            Transition Metal Titanium Compoment (II)                                      Component (mmol) 1                                                            Ethylene Pressure (kg/cm.sup.2 G)                                                              8                                                            Temperature (°C.)                                                                       80                                                           Time (min)       20                                                           Yield (g)        57.5                                                         ______________________________________                                         (Note)                                                                        1octene: 40 ml.                                                               Titanium component  II!: (tertiary                                            butylamido)dimethyl(tetramethylη.sup.5cyclopentadienyl)silanetitanium     dichloride.                                                              

                  TABLE 6                                                         ______________________________________                                                              Comp. Example 1                                         ______________________________________                                        Density (g/cm.sup.3)    0.868                                                 Branching Degree        0.052                                                 Weight-Average Molecular Weight  Mw!                                                                  230,000                                               Molecular Weight Distribution  Mw/Mn!                                                                 9.9                                                   Activation Energy of Melt Flow  Ea! (kcal/mol)                                                        7.5                                                   Melting Point (°C.)                                                                            56.4                                                  ______________________________________                                    

EXAMPLE 11

(1) Preparation of titanium catalytic component

A titanium catalytic component was prepared in the same manner as inExample 1-(1).

(2) Preparation of methylaluminoxane

The same procedure as in Example 1-(2) was repeated to preparemethylaluminoxane.

(3) Preparation of catalytic component

A 50-ml flask was dried and purged with nitrogen, and 20 ml of toluene,0.5 mmol of the titanium catalytic component prepared in theabove-mentioned (1) and 0.02 mmol of (tertiarybutylamido)dimethyl(tetramethyl-η⁵ -cyclopentadienyl)silanetitaniumdichloride were placed in the flask, followed by stirring at 25° C.Afterward, 0.6 mmol of methylaluminoxane prepared in the above-mentioned(2) was added, and reaction was then carried out for 2 hours.

The resultant reaction product was used as the catalytic component.

(4) Preparation of ethylene/1-octene copolymer

In a 1-liter stainless steel pressure-resistant autoclave were placed400 ml of toluene, 20 ml of 1-octene and 30 mmol of themethylaluminoxane prepared in the above-mentioned (2), and the mixturewas then heated up to 90° C. Afterward, 0.026 mmol, in terms oftitanium, of the catalytic component prepared in the above-mentioned (3)was added thereto.

Next, ethylene was continuously fed to the autoclave under a pressure of3.0 kg/cm² G to carry out polymerization reaction for 60 minutes.

After the completion of the polymerization reaction, the pressure wasreleased, and the resultant ethylene-1-octene copolymer was collected,washed with methanol, and then dried to obtain 75.2 g ofethylene-1-octene copolymer.

(5) Evaluation of ethylene-1-octene copolymer

(a) Structure analysis by NMR

The measurement of ¹³ C-NMR was carried out, and as a result, anyabsorption of a methyl group in the vicinity of a quaternary carbon atomwhich would be observed in an LDPE was not observed at 8.15 ppm.

(b) Measurement of density

Measurement was made in the same manner as in Example 1-(4)-(d). As aresult, the density was 0.895 g/cm³. In addition, the annealingtreatment of the sample was not carried out.

(c) Measurement of molecular weight distribution

Measurement was carried out in the same manner as in Example 1-(4)-(f),and as a result, a weight-average molecular weight (Mw) was 126,000, anumber-average molecular weight (Mn) was 45,000, and an Mw/Mn was 2.8.

(d) Measurement of activation energy (Ea) of melt flow

Measurement was carried out in the same manner as in Example 1-(4)-(g),and as a result, an activation energy (Ea) was 13.2 kcal/mol.

(e) Measurement of die swell ratio

A die swell ratio (DR) was obtained as (D₁ /D₀) by measuring a diameter(D₁, mm) of a strand formed by extrusion through a capillary nozzlediameter (D₀)=1.275 mm, length (L)=51.03 mm, L/D₀ =40, and entranceangle=90°) at an extrusion speed of 1.5 mm/min (shear rate=10 sec⁻¹) ata temperature of 190° C. by the use of a capillograph made by Toyo SeikiSeisakusho Co., Ltd., and then dividing this diameter by the diameter ofthe capillary nozzle.

The diameter (D₁) of the strand was an average value of values obtainedby measuring long axes and short axes of central portions of 5 sampleshaving a extruded strand length of 5 cm (a length of 5 cm from a nozzleoutlet).

As a result, the die swell ratio was 1.52.

EXAMPLE 12

(1) Preparation of titanium catalytic component

The same procedure as in Example 1-(1) was carried out except that 0.56g of cyclopentanol was replaced with 0.49 g of n-butanol, therebypreparing a titanium catalytic component.

(2) Preparation of catalytic component

The same procedure as in Example 11-(3) was repeated except that thetitanium catalytic component obtained in Example 11-(1) was replacedwith 0.25 mmol of the titanium catalytic component obtained in theabove-mentioned (1) and 0.01 mmol of (tertiarybutylamido)dimethyl(tetramethyl-η⁵ -cyclopentadienyl)silanetitaniumdichloride and 0.8 mmol of methylaluminoxane were used, therebypreparing a catalytic component.

(3) Preparation of ethylene/1-hexene copolymer

The same procedure as in Example 11-(4) was carried out under conditionsshown in Table 7 except that 10 ml of 1-hexene was used in place of1-octene, thereby preparing ethylene/1-hexene copolymer. The result areshown in Table 7.

The measurement of ¹³ C-NMR was carried out, and as a result, anyabsorption of a methyl group in the vicinity of a quaternary carbon atomwhich would be observed in an LDPE was not observed at 8.15 ppm.

COMPARATIVE EXAMPLE 2

The same procedure as in Example 12-(3) was carried out under conditionsshown in Table 7, thereby preparing ethylene/1-hexene copolymer. Theresult are shown in Table 7.

                  TABLE 7 (I)                                                     ______________________________________                                                              Comp.                                                                 Example 12                                                                            Example 2                                               ______________________________________                                        Toluene (ml)    400       400                                                 MAO (mmol)      30        10                                                  Catalyst (mmol) 0.26      0.01                                                Temperature (°C.)                                                                      90        150                                                 Ethylene         3         8                                                  (kg/cm.sup.2 G)                                                               Time (min)      60        30                                                  Yield (g)       52.7      52.3                                                ______________________________________                                         MAO: Methylaluminoxane.                                                       Catalyst of Example 12: Catalytic component prepared in Example 12(2).        Catalyst of Comparative Example 2: (Tertiary                                  butylamido)dimethyl(tetramethyl-η.sup.5cyclopentadienyl)silanetitaniu     dichloride.                                                              

                  TABLE 7 (II)                                                    ______________________________________                                                                Comp.                                                                 Example 12                                                                            Example 2                                             ______________________________________                                        Density (g/cm.sup.3)                                                                            0.902     0.937                                             Weight-Average                                                                Molecular Weight  Mw!                                                                           45,000    62,000                                            Molecular Weight  3.2       3.8                                               Distribution  Mw/Mn!                                                          Activation Energy 12.5      11.5                                              of Melt Flow  Ea!                                                             (kcal/mol)                                                                    Die Swell Ratio  D.sub.R !                                                                      1.40      1.06                                              ______________________________________                                    

EXAMPLE 13

The ethylene/1-octene copolymer obtained in Example 11 was hydrogenatedunder conditions of a temperature of 140° C., a copolymer concentrationof 9% by weight, a hydrogen pressure of 30 kg/cm² G, a carbon-supportingruthenium catalyst (a Ru content=5% by weight) concentration of 4% byweight and a reaction time of 6 hours in a decalin solvent, and theobtained polymer was then isolated from the reaction solution.

From this copolymer, a hot pressed sheet having a thickness of 300 μmwas formed, and an infrared absorption spectrum was then measured. As aresult, any absorption of unsaturated groups present in the range of 885to 970 cm⁻¹ was not observed.

In addition, density, molecular weight, a melting point and fluidactivation energy were the same as in Example 11.

EXAMPLE 14

(1) Preparation of catalytic component

A catalytic component was prepared in the same manner as in Example1-(1).

(2) Preparation of methylaluminoxane

The same procedure as in Example 1-(2) was repeated to preparemethylaluminoxane.

(3) Polymerization of ethylene/1-hexene copolymer

Under a nitrogen atmosphere, 400 ml of toluene, 20 ml of 1-hexene and0.25 ml of a triisobutylaluminum solution in toluene (2 mols/l) wereplaced in a 1-liter flask equipped with a stirrer, followed by stirringat 20° C. for 5 minutes. Afterward, 10 mmols of methylaluminoxaneprepared in the above-mentioned (2) was added thereto, and the solutionwas heated up to 70° C. Next, 1.5 ml of the titanium catalytic componentprepared in the above-mentioned (1) and 2 micromols of (tertiarybutylamido)dimethyl(tetramethyl-η⁵ -cyclopentadienyl)silanetitaniumdichloride were added, and ethylene was fed under a partial pressure of7.5 kg/cm² G to initiate polymerization. While the total pressure wasconstantly maintained, reaction was carried out at 70° C. for 30minutes.

After the completion of the reaction, the pressure was released, and theresultant reaction product was thrown into methanol and then filtered tocollect the polymer. Next, this polymer was dried at 85° C. for 10 hoursunder reduced pressure. As a result, 60.5 g of ethylene-1-hexenecopolymer was obtained.

(4) Evaluation of ethylene-1-hexene copolymer

(a) Evaluation of thermal behavior

Measurement was made in the same manner as in Example 1-(4)-(c), and asa result, a crystallization enthalpy (ΔH) was 80 J/g and a melting point(Tm) was 104.0° C.

(b) Density

Measurement was made in the same manner as in Example 1-(4)-(d). As aresult, the density was 0.902 g/cm³. In addition, the annealingtreatment of the sample was not carried out.

(c) Measurement of molecular weight distribution

Measurement was carried out in the same manner as in Example 1-(4)-(f),and as a result, a ratio Mw/Mn of a weight-average molecular weight to anumber-average molecular weight was 7.79.

(d) Measurement of intrinsic viscosity

An intrinsic viscosity was measured in decalin at 135° C., and as aresult, the intrinsic viscosity η! was 2.42 dl/g.

(e) Evaluation of non-Newtonian properties

As a device, an RMS E605 model made by Rheometrics Co., Ltd. wasemployed, and sinusoidal vibration was given at 190° C. in a strainquantity of 10% to measure dynamic viscoelastic properties, whereby amelt viscosity η! and a shear rate o dependence were obtained andnon-Newtonian properties were evaluated. The results are shown in FIG.3. In addition, the activation energy of melt flow was 12.2 kcal/mol.

(5) Measurement of Huggins coefficient (k)

The viscosities of the ethylene copolymer were measured in a dilutesolution state, and a Huggins coefficient (k) was then calculated inaccordance with the viscosity equation

    η.sub.sp /c= η!+k η!.sup.2 c.

Reduced viscosities η_(sp) /c were measured changing the polymerconcentration c in a decalin solvent at 135° C. at 5 or more points in arange in which a linear relation was recognized. A linear coefficient ofcorrelation was 0.995 or more. Here, η! is a intrinsic viscosity. TheHuggins coefficient (k) was 0.439.

(6) Evaluation of film

The tensile modulus, the breaking strength and the elongation of a filmwere 760 kg/cm², 420 kg/cm² and 660%, respectively.

(7) Evaluation of catalyst

(a) Evaluation 1 of catalyst

The ethylene polymerization properties of the titanium catalyticcomponent prepared in the above-mentioned (1) were evaluated bypreparing polyethylene in the same manner as in the above-mentioned (3)except that (tertiary butylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitanium dichloride and 1-hexene were not usedand the partial pressure of ethylene was set to 6 kg/cm² G, and thendetermining terminal vinyl groups.

(Measurement of terminal vinyl groups)

A pressed sheet having a thickness of 100 μm was formed, and atransmitted infrared absorption spectrum was measured. The number n ofterminal vinyl groups was calculated on the basis of an absorbance(A₉₀₇) based on the terminal vinyl groups in the vicinity of 907 cm⁻¹, afilm thickness (t) and a resin density (d) in accordance with theequation

    n=0.114A.sub.907 / d·T!

wherein d=g/ml, T=mm, and n=the number of the vinyl groups with respectto 100 carbon atoms. As a result, the number of terminal vinyl groupswas 4.5 groups/1,000 carbon atoms.

(b) Evaluation 2 of catalyst (Evaluation of copolymerization properties)

The copolymerization of ethylene and 1-octene was carried out in thepresence of (tertiary butylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitanium dichloride under conditions shown inTable 8, and the crystallization enthalpy (ΔH) and the melting point(Tm) of the resultant copolymer were then measured. The measured resultsare shown in Table 8.

                  TABLE 8 (I)                                                     ______________________________________                                                         No. 1                                                                              No. 2                                                   ______________________________________                                        Toluene (ml)       400    400                                                 TIBA.sup.4) (mmol) 0.5    0.5                                                 MAO (mmol)         10     10                                                  Metallic            2      2                                                  Compound (μmol)                                                            Temperature (°C.)                                                                         70     80                                                  Monomer Charge                                                                Ratio.sup.3)  M!   0.231  0.248                                               Time (min)         10     10                                                  ______________________________________                                    

                  TABLE 8 (II)                                                    ______________________________________                                                        No. 1 No. 2                                                   ______________________________________                                        Yield (g)         16.5    19.2                                                TM.sup.4) (°C.)                                                                          93.6    90.4                                                ΔH.sup.5) (J/g)                                                                              75      61                                               ΔH · Tm                                                                           7,020   5,514                                              ΔH · Tm calculated                                                               17,492  17,107                                              in accordance with                                                            a general equation.sup.6)                                                     ______________________________________                                         .sup.1) TIBA: Triisobutylaluminum.                                            .sup.2) MAO: Methylaluminoxane prepared in Example 14(2).                     .sup.3) This was calculated on the basis of the weight of ethylene            dissolved at polymerization temperature in a mixed solvent of 400 ml of       toluene and 7.15 g of 1octene at 25° C.                                .sup.4) Tm: Melting point, which was measured in the same manner as in        Example 14(4).                                                                .sup.5) (ΔH): Crystallization enthalpy, which was measured in the       same manner as in Example 14(4).                                              .sup.6) ΔH · Tm: This was calculated in accordance with        27000-21600  M!.sup.0.56.                                                     .sup.7) (Tertiary                                                             butylamido)dimethyl(tetramethylη.sup.5cyclopentadienyl)silanetitanium     dichloride                                                               

The copolymerization was accomplished in accordance with Example 14-(3),but the metallic compound was added after ethylene was dissolved to asaturation state at the polymerization temperature, whereby thepolymerization was started.

Concretely, evaluation was made by the use of the following device andmethod.

That is to say, as a polymerization reactor, there was used apressure-resistant stainless steel autoclave having a volume of 1.76liters and an inner diameter of 114 mm. This autoclave was equipped withan anchor blade (thickness=1.5 mm) as a stirrer, and a space between theend of the blade and the inner wall of the reactor was 17 mm at theclosest position. In addition, the area of one surface of the blade wasabout 13 cm². The blade, when used, was fixed in such a state that 70%or more of the blade area might be immersed in a solvent.

As the procedure of the evaluation, the above-mentioned autoclave wassufficiently dried, and 400 ml (volume at 25° C.) of dry toluene(moisture content=5 ppm or less) was thrown into the autoclave at roomtemperature under a nitrogen atmosphere and a predetermined amount byweight of 1-octene (water content=5 ppm or less) was further thrown. Inaddition, as a catalytic component, an organic metallic compound (e.g.,aluminoxane, an alkylaluminum or the like) was thrown thereinto.Afterward, the solution was stirred at room temperature for 3 minutes.Next, the solution was heated up to polymerization temperature in asealing state, and after pressure had reached a constant level, ethylenewas introduced into the autoclave. Then, the feed of ethylene wasstopped, and a saturation state was confirmed by a fact that anypressure did not drop.

At this time, a stirring velocity was constantly 500 rpm. While thiscondition was maintained, the metallic compound to be evaluated whichwas another catalytic component was added thereto, thereby initiatingcopolymerization.

After the initiation of the copolymerization, it was necessary that theflow rate of ethylene should be controlled to 3 normal liters/minute orless under a predetermined pressure and the temperature should be within±2° C. of a predetermined polymerization temperature.

If such a control is not accomplished, it is required that the amount ofthe catalyst is changed so as to make the evaluation again.

After the copolymerization had been carried out for a certain time, thefeed of ethylene was stopped, and the pressure was immediately releasedto remove unreacted ethylene. Afterward, deactivation was done withmethanol.

In this case, the total amount of the solvent in the catalyticcomponents was adjusted so as to be 1% or less based on the total volumeof toluene and 1-octene which were the polymerization solvents.

COMPARATIVE EXAMPLE 3

The same procedure as in Example 14 was repeated except that thetitanium catalytic component prepared in Example 14-(1) was not used,thereby preparing 43.5 g of ethylene/1-hexene copolymer. The results ofevaluation were as follows.

Melting point (Tm): 75.0° C.

Density: 0.908 g/cm³

Intrinsic viscosity η!: 2.32 dl/g

Molecular weight distribution (Mw/Mn): 6.99

Crystallization enthalpy (ΔH): 50 J/g

Huggins coefficient (k): 0.345

Furthermore, the shear rate ω dependence of a melt viscosity η! wasobtained in the same manner as in Example 14-(4)-(e), wherebynon-Newtonian properties were evaluated. The results are shown in FIG.3.

EXAMPLE 15

80% by weight of ethylene/1-butene copolymer (density=0.920 g/cm³,MI=1.0 g/10 min) and 20% by weight of ethylene/1-hexene copolymer inExample 14 were molten and kneaded at 190° C. for 5 minutes at 50 rpm bythe use of a laboblast mill (Toyo Seiki Seisakusho Co., Ltd., internalvolume=30 ml) to obtain a resin composition.

From this resin composition, a film having a thickness of 100 μm wasformed. The physical properties of the thus formed film were as follows.

Tensile modulus: 2,000 kg/cm²

Breaking strength: 380 kg/cm²

Elongation: 670%

Possibility of Industrial Utilization

An ethylene copolymer of the present invention is derived from ethyleneand an olefin having 3 to 20 carbon atoms and does not contain anyquaternary carbon in the main chain of the polymer, and it is differentfrom a usual HDPE, L-LDPE and LDPE. The ethylene copolymer ischaracterized in that the activation energy of melt flow can becontrolled, working properties are excellent, and physical propertiessuch as density, melting point and crystallinity can be controlled.Furthermore, the ethylene copolymer subjected to a hydrogenationtreatment not only has the above-mentioned characteristics but also isexcellent in thermal stability.

Furthermore, according to a process for preparing the ethylene copolymerof the present invention, the ethylene copolymer can efficiently beprepared in which the activation energy of melt flow and a Hugginscoefficient can be controlled and non-Newtonian properties are improvedand working properties are excellent.

We claim:
 1. An ethylene copolymer which is derived from ethylene and anolefin having 3 to 20 carbon atoms and in which (1) any quaternarycarbon atom is not present in a polymeric main chain; (2) the activationenergy (Ea) of melt flow is in the range of 8 to 20 kcal/mol; and (3) aratio between Huggins coefficients (k) of the copolymer and astraight-chain ethylene polymer having the same intrinsic viscosity η!measured at a temperature of 135° C. in a decahydronaphthalene solventmeets the relation of the equation

    1.12<k.sup.1 /k.sup.2 ≦5

wherein k¹ is the Huggins coefficient of the copolymer, and k² is theHuggins coefficient of the straight-chain ethylene polymer.
 2. Anethylene copolymer which is derived from ethylene and an olefin having 3to 20 carbon atoms and in which (1) any quaternary carbon atom is notpresent in a polymeric main chain; (2) the activation energy (Ea) ofmelt flow is in the range of 8 to 20 kcal/mol; and (3) a molar ratio CH₃/CH₂ ! of a methyl group in a region of 0.8 to 1.0 ppm to a methylenegroup in a region of 1.2 to 1.4 ppm observed by a proton nuclearmagnetic resonance spectrum method (¹ H-NMR) is in the range of 0.005 to0.1, and a melting point (Tm) and the molar ratio CH₃ /CH₂ ! observed bya differential scanning calorimeter (DSC) meet the equation

    Tm≧131-1,340 CH.sub.3 /CH.sub.2 !.


3. 3. An ethylene copolymer which is derived from ethylene and an olefinhaving 3 to 20 carbon atoms and in which (1) any quaternary carbon atomis not present in a polymeric main chain; (2) the activation energy (Ea)of melt flow is in the range of 8 to 20 kcal/mol; and (3) the relationbetween a weight-average molecular weight (Mw) in terms of thepolyethylene measured by a gel permeation chromatography method and adie swell ratio (DR) meet the equation

    DR>0.5+0.125×log Mw.


4. The ethylene copolymer according to claim 1, wherein theweight-average molecular weight (Mw) in terms of the polyethylenemeasured by the gel permeation chromatography method is in the range of5,000 to 2,000,000.
 5. The ethylene copolymer according to claim 1wherein a ratio Mw/Mn of the weight-average molecular weight (Mw) to anumber-average molecular weight (Mn) in terms of the polyethylenemeasured by the gel permeation chromatography method is in the range of1.5 to
 70. 6. The ethylene copolymer according to claim 1 wherein aresin density is in the range of 0.85 to 0.96 g/cm³.
 7. A thermoplasticresin composition which comprises the ethylene copolymer described inclaim
 1. 8. The process for preparing an ethylene copolymer according toclaim 7 wherein the homopolymerization of ethylene or thecopolymerization of ethylene and at least one member selected fromolefins having 3 to 20 carbon atoms is carried out in the presence of acatalyst comprising the components (b) and (c) to substantially producea polymer, and the catalytic component (a) is then added to thepolymerization system to carry out copolymerization.
 9. The process forpreparing an ethylene copolymer according to claim 8 wherein each of thetransition metal compounds which are the components (a) and (b) is oneor more of compounds containing a metal selected from the groupconsisting of titanium, zirconium, hafnium, chromium, vanadium andmetals in the lanthanide series.
 10. The process for preparing anethylene copolymer according to claim 8 wherein each of the transitionmetal compounds which are the components (a) and (b) is one or more ofcompounds containing a metal selected from the group consisting oftitanium, zirconium, hafnium, chromium, vanadium and metals in thelanthanide series.
 11. A process for preparing an ethylene copolymerwhich comprises the step of copolymerizing ethylene and at least onemember selected from olefins having 3 to 20 carbon atoms in the presenceof a catalyst comprising (a) a transition metal compound selected fromtransition metal compounds that provide a relation between a monomercharge composition when using ethylene and 1-octene having a molar ratioM! of 1-octene/(ethylene+1-octene), and the product of a crystallizationenthalpy (ΔH) and a melting point (Tm) of the produced copolymer thatmeets the equation

    0≦ΔH·Tm≦27,000-21,600  M!.sup.0.56

(under polymerization conditions using the component (a) together withan aluminoxane), (b) a transition metal compound capable of forming aterminal vinyl group in the homopolymerization of ethylene or thecopolymerization of ethylene and at least one member selected fromolefins having 3 to 20 carbon atoms (under polymerization conditionsusing the component (b) together with the aluminoxane), and (c) acompound capable of forming an ionic complex from the abovementionedcomponents (a) and (b) (the transition metal compounds of the components(a) and (b) are compounds containing metals in the groups 3 to 10 or alanthanide series of the periodic table) wherein component (a) andcomponent (b) are different from one another.
 12. The process forpreparing an ethylene copolymer according to claim 11 wherein thecomponent (c) is a coordination compound comprising a cation and ananion which is constituted of plural groups bonded to the element. 13.The process for preparing an ethylene copolymer according to claim 11wherein the component (a) is a compound represented by the formula (I),(III), (VI) or (XIII), and the component (b) is a compound representedby formula (I) or formula (IV), wherein each of the compounds of formula(I) and (IV) contain an alkoxy group, or (b) is a compound representedby formula (II) or (III);

    CpM.sup.1 R.sub.a.sup.1 R.sub.b.sup.2 R.sub.c.sup.3        (I)

    Cp.sub.2 M.sup.1 R.sub.a.sup.1 R.sub.b.sup.2               (II)

    (Cp-Ae-Cp)M.sup.1 R.sub.a.sup.1 R.sub.b.sup.2              (III)

    M.sup.1 R.sup.1 .sub.a R.sup.2 .sub.b R.sup.3 .sub.c R.sup.4.sub.d(IV) ##STR23## wherein M.sup.1 represents a transition metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium and chromium, Cp is a member selected from the group consisting of cyclopentadienyl, substituted cyclopentadienyl, indenyl, substituted indenyl, tetrahydroindenyl, substituted tetrahydroindenyl, fluorenyl and substituted fluorenyl, wherein one or more carbon atoms in the skeleton of the cyclopentadienyl group may be substituted by a hetero-atom, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each, independently, a σ-bond ligand, a chelate ligand or a Lewis base, A represents a cross-linkage by a covalent bond; a, b, c and d each is independently an integer of 0 to 4, and e is an integer of 0 to 6; wherein two or more of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 may bond to each other to form a ring; wherein when Cp has a substituent, the substituent is an alkyl group having 1 to 20 carbon atoms; and wherein in the formulae (II) and (III), the two Cps may be the same or different from each other;

M³ represents a titanium atom, a zirconium atom or a hafnium atom; X²represents a hydrogen atom, a halogen atom, an alkyl group having 1 to20 carbon atoms, an aryl group, an alkylaryl group or an arylalkyl grouphaving 6 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbonatoms; Z represents SiR⁷ ₂, CR⁷ ₂, SiR⁷ ₂ SiR⁷ ₂, CR⁷ ₂ CR⁷ ₂, CR⁷ ₂ CR⁷₂ CR⁷ ₂, CR⁷ ═CR⁷, CR⁷ ₂ Si⁷ ₂ or GeR⁷ ₂, and Y² represents --N(R⁶)--,--O--, --S-- or --P(R⁶)--; wherein R⁷ is a group selected from the groupconsisting of a hydrogen atom, an alkyl group having 20 or lessnon-hydrogen atoms, an aryl group, a silyl group, a halogenated alkylgroup, a halogenated aryl group and a combination thereof, and R⁶ is analkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10carbon atoms, or R⁶ may form a condensed ring of one or more R⁷ s and 30or less non-hydrogen atoms; w represents 1 or 2; E¹ and E² are each ahydrocarbon group having 1 to 20 carbon atoms, v and x are each 0 or 1,and E¹ and E² form a crosslinking structure via Y⁴ ; E³ and E⁴ are eacha σ-bond ligand, a chelate ligand or a Lewis base, and may be the sameor different from each other; v' and x' are each an integer of 0 to 2,wherein v'+x'=(valence of M¹ -2); Y⁴ is a hydrocarbon group having 1 to20 carbon atoms, E⁵ E⁶ Y⁵, an oxygen atom or a sulfur atom, and m is aninteger of 0 to 4; E⁵ and E⁶ are each a hydrocarbon group having 1 to 20carbon atoms, and Y⁵ is a carbon atom or a silicon atom.
 14. The processfor preparing an ethylene copolymer according to claim 13 wherein thecomponent (a) is a compound represented by the formula (III) or (VI),and the component (b) is a compound represented by formulas (I), (II),(III) or (IV), wherein the compounds of formulas (I) and (IV) eachcontain an alkoxy group.
 15. The process for preparing an ethylenecopolymer according to claim 13 wherein the component (a) is a compoundrepresented by the formula (III) or (VI), and the component (b) is acompound represented by formulas (I), (III) or (IV), wherein thecompounds of formulas (I) and (IV) each contain an alkoxy group.
 16. Anethylene copolymer, prepared by subjecting to a hydrogenation treatment,a copolymer derived from ethylene and an olefin having 3 to 20 carbonatoms and in which (1) any quaternary carbon atom is not present in apolymeric main chain; (2) the activation energy (Ea) of melt flow is inthe range of 8 to 20 kcal/mol; and (3) a ratio between Hugginscoefficients (k) of the copolymer and a straight-chain ethylene polymerhaving the same intrinsic viscosity η! measured at a temperature of 135°C. in a decahydronaphthalene solvent meets the relation of the equation

    1.12≦k.sup.1 /k.sup.2 ≦5

wherein k¹ is the Huggins coefficient of the copolymer, and k² is theHuggins coefficient of the straight-chain ethylene polymer.